Solar Photochemical Synthesis - American Chemical Society

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Solar Photochemical Synthesis: From the Beginnings of Organic Photochemistry to the Solar Manufacturing of Commodity Chemicals Michael Oelgemöller* College of Science and Engineering, James Cook University, Townsville, Queensland 4811, Australia ABSTRACT: Natural sunlight offers a cost-efficient and sustainable energy source for photochemical reactions. In contrast to the lengthy and small-scale “flask in the sun” procedures of the past, modern solar concentrator systems nowadays significantly shorten reaction times and enable technical-scale operations. After a brief historical introduction, this review presents the most important solar reactor types and their successful application in preparative solar syntheses. The examples demonstrate that solar manufacturing of fine chemicals is technically feasible and environmentally sustainable. After over 100 years, Ciamician's prophetic vision of “the photochemistry of the future” as a clean and green manufacturing methodology has yet to be realized. At the same time, his warning “for nature is not in a hurry but mankind is” is still valid today. It is hoped that this review will lead to a renewed interest in this truly enlightening technology, that it will stimulate photochemists and photochemical engineers to “go back to the roots onto the roofs” and that it will ultimately result in industrial applications in the foreseeable future.

CONTENTS 1. Introduction 2. Solar Beginnings of Organic Photochemistry 3. Solar Reactor Technology 3.1. Non- and Low-Concentrating Reactors 3.1.1. Flatbed Reactors 3.1.2. Compound Parabolic Collectors 3.2. Concentrating Reactors 3.2.1. Parabolic Troughs 3.2.2. Dish Reactors 3.3. Highly Concentrating Reactors 4. Solar Photochemical Production of Fine Chemicals 4.1. Solar Reactions in Non- to Low-Concentrating Reactors 4.1.1. SOLFIN and Related Facilities 4.1.2. Other Devices 4.2. Solar Reactions in Moderately Concentrating Reactors 4.2.1. SOLARIS and PROPHIS Loops 4.2.2. Other Devices 4.3. Solar Reactions in Highly Concentrating Reactors 4.4. Solar Reactor Comparison Studies 5. Challenges and Future Opportunities 6. Concluding Remarks Author Information Corresponding Author Notes Biography Acknowledgments References

1. INTRODUCTION A photochemical reaction is a chemical reaction caused by absorption of ultraviolet, visible, or infrared radiation within a part of the substrate, that is, its chromophore.1,2 Subsequently, the substrate is promoted from its ground state to a higherenergy state, which can undergo various physical and chemical processes.3,4 These multiple pathways are typically summarized in a Jablonski diagram.5 Of the physical routes, fluorescence, phosphorescence, and internal conversion result in loss of excess energy and subsequently return to the ground state. Although these processes do not convert or consume the substrate, they are of significant importance in molecular spectroscopy. The excited-state energy can alternatively initiate a chemical reaction, such as an elimination, cleavage, rearrangement, isomerization, cyclization, addition, or electron transfer. Photochemical reactions include direct excitation, photosensitization, photocatalysis, photoinduced electron transfer (PET), and photoredox catalysis. Compared to many thermal methods, photochemical processes allow for easy construction of thermodynamically disfavored products such as small rings. They can furthermore overcome large activation barriers. Many photochemical reactions are additionally unique as their products are not accessible by other methods. Photochemistry has nowadays enriched the portfolio of synthetic chemistry through highly selective and efficient phototransformations.6−12 Photochemical methods are also frequently chosen as key steps in natural products syntheses.13−15 In addition, synthetic photochemistry is often considered a “green” and sustainable

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Special Issue: Photochemistry in Organic Synthesis Received: December 10, 2015 Published: May 11, 2016

© 2016 American Chemical Society

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DOI: 10.1021/acs.chemrev.5b00720 Chem. Rev. 2016, 116, 9664−9682

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methodology. 16−20 Some of the commonly mentioned operating features to justify this claim are as follows: • Initial absorption of light occurs localized within the chromophore and can be controlled with wavelength, even for multichromophoric compounds (“chromatic orthogonality concept”).2 • Activation of a compound often can be achieved by either direct or sensitized (catalyzed) pathways. • Energy input is directly controlled with wavelength. • The light itself does not produce any chemical waste that creates disposal problems. • Most photoreactions (except photoinduced chain reactions) can be terminated safely by turning off the light source. In contrast to these advantages, photochemical processes are often unsustainable due to limitations of the available technology, especially on technical scales,21,22 or unfavorable photophysics of the reaction. Some of the most common drawbacks include the following: • Strong light sources are dangerous to humans and require strict operating protocols such as shielding.23 Likewise, light can rapidly damage reactor materials, thus demanding costly replacements. • Conversion of electrical power into light comes with substantial heat generation, which requires energy- and water-intensive cooling. • Optical filters are often necessary to remove destructive emission wavelengths, hence reducing energy efficiency of the light sources. • Most artificial light sources have limited lifetimes and their renewal causes significant maintenance costs. • Complete light absorption is typically achieved within a thin layer of the reaction medium (as expressed in the Beer−Lambert law24), thus necessitating high dilutions and solvent needs. • Photochemical reactions require inert and transparent solvents and are therefore frequently performed in hazardous benzene, acetonitrile, carbon tetrachloride, dichloromethane, or methanol. • Typical batch processes suffer from subsequent degradation of photochemically unstable products, which lowers product qualities and yields. • Most photochemical transformations suffer from low quantum efficiencies due to dominant photophysical deactivation pathways.25 Exhaustive irradiation is therefore required in these cases in order to achieve complete conversion and subsequently high yields. For typical laboratory processes, monochromatic lasers,26 near-monochromatic excimers,27,28 or narrowly emitting LEDs (light-emitting diodes)29,30 are now available as alternative light sources that avoid the need for optical filters. Likewise, continuous-flow operation in microreactors has been shown to significantly reduce solvent needs and photodecomposition losses.31−36 Photochemical syntheses have also been demonstrated in less hazardous media such as water,37−39 micelles,40 ionic liquids,41 or supercritical CO2.42 Likewise, higher quantum efficiencies of photochemical transformations have been achieved by use of gaseous CO243,44 or N245 as leaving groups. Still, one of the major concerns and cost drivers for the chemical industry is the energy demand of its production processes.46−48 Due to the high energy needs of large artificial

light sources,49,50 photochemical manufacturing relies on inexpensive and readily available electricity. As a result, industrial photochemistry is limited to low-volume fine chemicals, for example, fragrances, flavors, or vitamins.51,52 The small volumes but relatively high market values of most photochemical products make natural sunlight an attractive energy and light source.53−56 For industrial applications, advanced solar reactors and concentrators should be implemented.57 Naturally, solar photochemistry is limited to those reactions that operate in the usable range of the solar spectrum, that is, between 300 and 700 nm. In general, sunlight at Earth’s surface consists of 3−5% ultraviolet ($10 (U.S.) per kilogram makes them furthermore attractive for photochemical processes. The majority of current preparative photochemical applications are consequently within the flavor, fragrance, and supplementary medicine (vitamins) industries.51,52 Of these, a variety of transformations are potentially transferable to solar conditions, that is, those that can be performed in the usable solar radiation range of 300−700 nm. Despite these obvious opportunities, the solar synthesis of chemicals has received little attention.127 In order to boost interest in this attractive technology, the following sections summarize selected examples of preparative photochemistry in advanced solar reactor systems. The reactions are presented by type of reactor used with key experimental details shown. Transformations that follow the “flask in the sun” approach76,77 or purely solar thermal syntheses are excluded from these examples.128−131 4.1. Solar Reactions in Non- to Low-Concentrating Reactors

4.1.1. SOLFIN and Related Facilities. The SOLFIN (solar synthesis of fine chemicals) loop is a simple solar chemical test facility operated at PSA in Almerı ́a, Spain. Similar solar modules have been used by other authors and are therefore included here. Dondi et al.132 launched a detailed study on homogeneous solar-sensitized additions to electrophilic alkenes and alkynes in the SOLFIN loop. Its horizontal parabolic trough was tilted at 35° toward the sun and produced a concentration factor of approximately 4 suns. The whole loop (Figure 9) had a capacity of 1.2 L and was operated in circulation mode. For easy removal of the photocatalyst during workup, water-soluble disodium benzophenonedisulfonate (BPSS) was applied. Various transformations were successfully completed with good to high conversion rates of 55−90% after reasonable exposure times of 4.5−14 h. In most cases, products were not purified and calculated yields ranged from 31% to 83%. An exception was the solar synthesis of terebic acid (10) from maleic acid (8a) and 2-propanol (9). Illumination for 14 h over a period of 3 days resulted in a high conversion of 90%, as determined by HPLC. Subsequent workup and isolation produced 10 in multigram quantities and in a yield of 75% (Scheme 3). The radiation conditions varied significantly during the solar experiment, with particularly poor solar conditions during the second day. A number of heterogeneous gas−liquid reactions were similarly performed in a different SOLFIN facility by Heller et al.133,134 The module had a reported optical concentration factor of 2 suns and a total volume of 1 L. The module was subsequently used for catalyzed [2 + 2 + 2]-cycloadditions to produce monosubstituted pyridines. Cyclopentadienyl-1,5cyclooctadiene-cobalt(I) [CpCoCOD] was chosen as a catalyst, and the reagent gas ethylene was introduced into the reaction mixture in a reservoir tank. An interesting example was the solar

Figure 9. (a) SOLFIN reactor at PSA in Almerı ́a, Spain, in 2000. (b) Schematic representation. Both panels reprinted with permission from ref 132. Copyright 2009 The Royal Society of Chemistry.

Scheme 3. Solar BPSS-Catalyzed Addition of 2-Propanol (9) to Maleic Acid (8a)

cycloaddition of chiral nitrile 11 (Scheme 4), which gave the optically pure pyridine derivate 12 in a moderate chemical yield of 52% after approximately 6 h of solar exposure. The illumination could be conducted in water with small amounts of toluene as a cosolvent. The enantiopurity of product 12 was confirmed by HPLC analysis. A trace amount of benzene was determined to be the sole byproduct. Other alkyne−nitrile combinations gave the corresponding pyridine compounds in yields of 12−91%. A similar small-scale CPC reactor at the PSA in Spain was used by Covell et al.135 to perform the solar photo9670


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Scheme 4. Enantioselective Co(I)-Catalyzed [2 + 2 + 2]Cycloaddition of Nitrile 11 to Chiral Pyridine Derivative 12

Scheme 6. Solar TiO2-Catalyzed Addition of Silane 16 to Maleic Acid (8a) and Maleic Anhydride (8b)

cycloadditions of 2-acetoxy-1,4-naphthoquinone (13) with either styrene (14a) or 1,1-diphenylethene (14b) in acetonitrile (Scheme 5). The aluminum mirror of the reactor was able to

yields and excellent qualities of the alkylated products 17a,b in combination with the simple operation and option for recovery of solvent as well as photocatalyst clearly demonstrated the potential of solar heterogeneous photocatalysis. 4.1.2. Other Devices. An interesting example of continuous-flow photobromination in concentrated sunlight has recently been reported by Kim et al.140 (Scheme 7 and Figure

Scheme 5. Solar [2 + 2]-Cycloaddition of Styrene (14a) and 1,1-Diphenylethene (14b) to 2-Acetoxy-1,4-naphthoquinone (13)

Scheme 7. Solar Bromination of Toluene (18) to Benzyl Bromide (19) under Continuous-Flow Conditions

concentrate sunlight by a factor of 2 suns onto a Pyrex tube. The entire plant had a capacity of 1 L and was operated in circulation mode with integrated cooling. Solar exposure of the reaction mixture for 10 h gave almost complete conversion of quinone 13. Simple evaporation furnished the desired cyclobutanes 15a and 15b in excellent purities and essentially quantitative yields without the need for further purification. In contrast, irradiations with a 125 W medium-pressure mercury lamp in an immersion-well batch reactor produced large amounts of byproducts. After column chromatographic purification, 15a and 15b were furthermore isolated in significantly lower yields of roughly 50%. The solar process was found to be very robust and could tolerate higher quinone concentrations and operation temperatures of up to 60 °C without any drop in performances. This comparison study nicely demonstrates the softness of solar radiation over artificial light with large destructive UV content. TiO2 is a very effective photocatalyst that can be easily recovered from the product mixture by filtration. Although widely utilized in water treatment,136,137 it has also found limited applications in preparative photochemistry.138 Cermenati et al.139 have examined the TiO2-catalyzed addition of 4methoxybenzyl(trimethyl)silane (16) to maleic acid (8a) and maleic anhydride (8b) under solar conditions (Scheme 6). The reactions were conducted by pumping the corresponding slurries through a cooled reaction tube placed in the focal line of a parabolic trough reactor with an exposed reflective mirror surface of 0.2 m2. For maleic anhydride (8b), complete conversion was achieved after 10 h of circulation, and the addition product 17b was isolated in 65% yield. In contrast, maleic acid (8a) required a prolonged illumination of 22 h to achieve a similar outcome. Solar quantum yields were subsequently estimated and were found to be low, ca. 1% for 8a and 3% for 8b, respectively. Despite this limitation, the good

Figure 10. Experimental setup for continuous-flow bromination in concentrated sunlight at Chungnam National University in Daejon, Korea, in 2015. Reprinted with permission from ref 140. Copyright 2015 Commonwealth Scientific and Industrial Research Organisation.

10). A Fresnel lens focused sunlight onto a curled FEP (fluorinated ethylene propylene) capillary tube. After initial optimization experiments in a microscale reactor, a larger model that carried a capillary with inner diameter of 1 mm, length of 5 m, and working volume of approximately 4 mL was constructed. The capillary was placed inside a shallow Dewar 9671


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flask that acted as a simple reflector. During operation, the lens and flask were tilted toward the sun. The improvised design achieved a concentration factor of 4 suns. By use of a set of syringe pumps, solutions of toluene (18) and bromine in chloroform were injected into a T-mixer before entering the solar module. With a residence time of 90 s, high selectivity for monobromination was achieved and benzyl bromide (19) was obtained in good calculated yield of 82%. Repeated injections (16 times) allowed for synthesis of a multigram quantity of the desired 19. On the basis of these results, the reactor had an estimated daily productivity of 44.1 g. Solar photooxygenation of furfural in a continuous-flow reactor equipped with a mirror has recently been described by Nsubuga et al.141 Simple floating reactors have been developed by Zhao et al.106,142 and were used for sensitized solar isomerization studies of a series of dienes and trienes. The smaller “kickboard” model (Figure 11) had a hole cut out of its

Heterogeneous TiO2/Cu(II) photocatalytic production of benzaldehyde from benzyl alcohol has been studied by Spasiano et al.143 in a large CPC reactor of 39 L capacity. Under optimized operation conditions, a theoretical yield of 53.3% was reported. However, the authors did not provide any details on isolation or purification of the desired product, which limits the usefulness of this study. 4.2. Solar Reactions in Moderately Concentrating Reactors

Solar concentrators enable higher space−time yields due to an increase in available photons. In contrast, their dependence on direct sunlight and the need for solar tracking result in significant installation and operation costs. 4.2.1. SOLARIS and PROPHIS Loops. The SOLARIS (solar photochemical synthesis of fine chemicals) facility was an advanced parabolic trough system located at PSA in Spain. The collector had a concentration factor of 20 suns. With a capacity of 35−70 L, the plant enabled technical-scale syntheses. The reactor was dismantled in 1992 and re-erected in a modified version as the PROPHIS plant (Figure 6b) at DLR in Cologne, Germany.114 The SOLARIS facility was used by Esser et al.81 and Pohlmann et al.82 for a solar chemical campaign. Reactions were chosen to representatively cover the entire usable solar spectrum between 300 and 700 nm. Although the loop consisted of four troughs in series, only a single trough with a reflective area of 8 m2 was chosen for the study. Following this strategy, acetone-sensitized [2 + 2]-photocycloaddition of 5ethoxy-5H-furan-2-ones (22) with ethene (23) was initially investigated (Scheme 9).81 Acetone shows an absorption of

Figure 11. Floating “kickboard” reactor developed at the University of Hawaii in 2008. Reprinted with permission from ref 106. Copyright 2008 The Royal Society of Chemistry.

Scheme 9. Acetone-Sensitized Solar [2 + 2]-Cycloaddition of 5-Ethoxy-5H-furan-2-ones (22) with Ethene (23)

body, which was fitted with a holding rack for three large 30 mL test tubes. An exchangeable sunlight filter plate (Plexiglas or Pyrex) was screwed onto the top, whereas a bottom mesh allowed water to enter. Cover and holder were positioned so that the sample tubes remained about half submerged in water. A larger reactor with a total holding volume of up to 400 mL was constructed from a “boogie-board” but with its test tubes secured and held in place by thin wires. Both reactor models operated without any need for external power and solely utilized natural or artificial water reservoirs for cooling. The “kickboard” was subsequently adopted for rose bengalsensitized isomerization of C15-nitrile 20 (Scheme 8).106 A Plexiglas cover with a cutoff at 400 nm was additionally chosen. The reaction was complete after just 15 min of solar illumination. After column chromatographic purification, a 1:1.1 isomeric mixture of cis-21 and di-cis-21 was obtained in a yield of 92%. Both solar floats were successfully applied to other solar isomerizations and various scales.

83% were achieved within 12 h of exposure. From these experiments, juglone (40) was isolated in 54−79% yields.152 Additional solar syntheses were conducted with highly reflective eloxated aluminum sheets as mirrors. A series of soluble and solid-supported sensitizers were subsequently tested in a variety of solvents with a standard exposure time of 4 h. The combination of rose bengal and either 2-propanol or acetone gave the highest yields for 40 of 75% and 79%, respectively.161 The same authors realized the solar synthesis of 40 in a simple parabolic trough reactor based on a Liebig condenser.164 Solar illuminations for 2.5−4.5 h achieved high conversions and produced juglone 40 in yields of 46−71%.

Figure 12. Solar line-focusing reactors on the roof of MPI in Mülheim, Germany, around 1994.

conditions required an extended exposure of 104 h and furnished a significantly lower yield of 75% for 38.

4.3. Solar Reactions in Highly Concentrating Reactors

Highly solar concentrators have seen practical applications in the solar thermal production of hydrogen.165,166 While solar synthesis in highly concentrated sunlight can potentially reach high space−time yields, the high temperatures created cause extreme heat stresses on reactor materials. In addition, engineering of the reactor vessel and cooling cycle is challenging and costly. Iċ ļ i and co-workers167,168 investigated a number of catalytic solar dehydrogenation reactions in a solar dish unit (Figure 7). A focusing mechanism allowed for solar concentrations of 40− 150 suns. By use of a copper(II) pivalate (CuPiv2) catalyst and benzophenone (BP) as a sensitizer, abietic acid and α-terpinene could be successfully converted into dehydroabietic acid and pcymene. In contrast, the solar conversion of acenaphthene reached low conversion rates, below 2.2%, even after extended exposure at 110 suns. Dehydrogenation of α-terpinene (6) to pcymene (41) was more successful, with conversion of 73% after 4 h of illumination with a concentration of 40 suns (Scheme 17). At the end of the reaction, the final product contained 47% of the desired dehydrogenated product 41.167

Scheme 15. Sensitized Solar Di-π-methane Rearrangement of 37 in Micellar Solution

A laboratory-scale parabolic trough reactor (Figure 6a) was employed by Oelgemöller et al.152,161 to study the photooxygenation of 1,5-dihydroxynaphthalene (39) to juglone (40) (Scheme 16). The trough focused direct sunlight onto the horizontal reaction tube with approximately 15 suns. An uneven liquid−gas slug flow was generated by injecting oxygen gas into the solvent stream in a simple Y-connector. Initially, the device was equipped with a holographic mirror that 9674


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Scheme 17. Solar Dehydrogenation of α-Terpinene (6) to pCymene (41)

Scheme 19. Solar Photooximation of Cyclohexane (44) and Subsequent Conversion to ε-Caprolactam (47)

The solar furnace facility at DLR in Germany (Figure 8) was used by Pohlmann et al.82 for solar synthesis in highly concentrated sunlight. A specialized reactor block was developed to withstand the high concentration factor of over 1000 suns inside the solar beam. The device had a cylindrical metal casing, which was separated into an IR filter cell in the front and a reaction cell in the back with quartz glass panels. The reaction mixture was pumped through the cell and cooled externally by an effective heat exchanger. The progress of the solar reaction was monitored by online UV spectroscopy. The device was applied to diastereoselective Paternò−Büchi addition of (−)-menthyl 2-thienylglyoxylate (41) to furan (42) (Scheme 18).82 At a liquid flow rate of 20 L·min−1, the reaction temperature could be maintained below 30 °C, and high conversions to the isomeric oxetane adducts 43a and 43b were achieved within 1.5−2 h. The solar transformations were remarkably clean and no byproducts could be detected in the final product mixture. Compared to conventional laboratory reactions, diastereoselectivity was similar, being 58% in favor of 43a. Despite the high concentration factor, the calculated usable solar photon yields were low, just 3−4%. This was likely caused by the northern location of the DLR site and the less favorable solar light conditions in October. Funken et al.169 have chosen the solar furnace at DLR to investigate the photooximation of cyclohexane (44) to cyclohexanone oxime hydrochloride (46) (Scheme 19). The reaction is of significant industrial importance for the synthesis of ε-caprolactam (47) and consequently nylon-6. For 1991, an annual production of 160 000 t was realized by Toray in Japan.51 The solar reaction was performed in a specialized titanium vessel that was fitted with glass windows for the incoming and exiting solar beam. The device was encased by a glass cooling water mantle, which also functioned as an effective IR filter. Cyclohexane (44) was initially saturated with hydrochloric acid before a fine stream of nitrosyl chloride (45) entered the reactor vessel from the bottom. During solar exposure, cyclohexanone oxime hydrochloride (46) precipitated as an oily substance. Solar exposure for 1−4.25 h furnished the desired 46 in good yields of 61−84% and with excellent selectivity. The photooximation was likewise investigated by Talukdar et al.170 using simulated sunlight.

The solar furnace at DLR in Germany was furthermore applied to photooxygenation of β-pinene (48) (Scheme 20).171 Scheme 20. Solar Photooxygenation of β-Pinene (48) and Subsequent Conversion to Myrtenol (50)

The transformation is industrially relevant in the fragrance industry for the synthesis of myrtenol (50).52 The photooximation reactor was modified to allow for oxygen feeding (Figure 13). Although high conversion of 48 of up to 97% could be achieved within 14 h, no isolated yields for the allylic hydroperoxide 49 or myrtenol (50) were provided. However, compared to photooxygenations in conventional laboratory equipment or the SOLARIS loop, the solar furnace gave significantly higher space−time yields. 4.4. Solar Reactor Comparison Studies

Several experimental campaigns have been conducted to compare the effectiveness of different solar reactor types and to determine the most suitable model for a specific location. Concentrating solar reactors depend on direct sunlight and are thus advantageous for countries with high levels of natural sunshine. In contrast, non- to low-concentrating reactors can harvest diffuse sunlight, which makes them preferable for operations in less sunny countries.100 Heinemann et al.172 compared the performances of a circulating solar trough reactor loop (Figure 12) and a static flatbed reactor in central Germany. The trough reactor achieved concentration factors of 5−60 suns and had an automatic suntracking mode, while the flatbed reactor was simply placed on the ground. Solar cyclization of the 1,1-dicarbonitrile 51 in a

Scheme 18. Diastereoselective Solar Paternò−Büchi Reaction of (−)-Menthyl 2-Thienylglyoxylate (41) with Furan (42)

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50% conversion, whereas a poor conversion of below 5% was achieved under overcast conditions after prolonged exposure of 6 h. In comparison, the less advanced flatbed system gave complete conversion under all three solar conditions. This superior performance was related to the ability of the flatbed to harvest diffuse sunlight, which makes up ca. 40% of the available sunlight in central Europe. The solar Paternò − Bü c hi reaction of (tert-butyl)phenylglyoxylate (53) with furan (42) in cyclohexane was realized in the SOLARIS loop at PSA in Spain and independently at the solar furnace at DLR in Germany (Scheme 22).81,82 Illumination with moderately concentrated Scheme 22. Solar Paternò−Büchi Reactions of (tertButyl)phenylglyoxylate (53) with Furan (42) in Two Different Concentrator Systems

mixture of acetonitrile and ethanol (27:1) and in the presence of 2,4,6-triphenylpyrylium tetrafluoroborate (TPPT) was subsequently selected as a model reaction (Scheme 21). Solar experiments were run under sunny, partially cloudy (ca. 60%), and completely overcast conditions. Under favorable sunny conditions, the advanced trough reactor gave complete conversion within 2 h and furnished the corresponding cyclization product 52 in 51% yield. In contrast, operation under partially cloudy settings for 3 h produced approximately

sunlight in the SOLARIS facility was conducted over a period of 2 days, during which the reaction mixture was kept at 20 °C. At a flow rate of 23 L·min−1, solar exposure for 17 h resulted in a conversion to the oxetane 54 of 32%.81 The reaction was subsequently repeated in the solar furnace with a concentration factor of >1000 suns inside the solar beam. Experiments reached conversions of 62−65% within 1−2 h of exposure. The usable solar photon yields were similar for both reactor types, which was explained by the difference in available UV content for the two locations. Schiel et al.150,173 studied the photoacylation of 1,4benzoquinone (55) with 2,4-dimethoxybenzaldehyde (56) in three different solar concentrator systems at DLR in Germany (Scheme 23). Under laboratory conditions, the reaction proceeded satisfactorily in tert-butanol and gave the acylated hydroquinone 57 in a yield of 66% after 18 h of irradiation.149 The reaction protocol was subsequently scaled up and

Scheme 21. TPPT-catalyzed Solar Cyclization of 1,1Dicarbonitrile 51 in Two Different Reactors

Scheme 23. Solar Acylations of 1,4-Benzoquinone (55) in Three Different Reactors

Figure 13. (a) Photooxygenation reactor in the solar furnace (DLR, Germany). Panel a reprinted with permission from ref 78. Copyright 2015 The Royal Society of Chemistry. (b) View toward the shutter window.

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5. CHALLENGES AND FUTURE OPPORTUNITIES Many reported solar chemical experiments simply transferred existing laboratory procedures outdoors.174 While this approach allowed for a direct comparison of lamp versus solar results, it commonly involved the usage of hazardous and flammable solvents, reagent gases, or catalysts. Due to the potential risks these materials represent to the environment, it is desirable to develop safer and more sustainable alternatives for solar chemical applications.175−177 This need was recently demonstrated by Ravelli et al.178 for photoredox catalytic reactions. While these transformations can use solar radiation, they are typically performed in toxic solvents and require the addition of large excess amounts of sacrificial reagents. The location of any future solar manufacturing facility will naturally depend on favorable year-round solar conditions as well as existing infrastructure and access to potential chemical markets. Thus, the Mediterranean region is often considered as a prime location for a synthetic-organic solar industry. Currently, the high development costs of solar factories and the natural dependency on the day−night cycle represent the biggest obstacles for technical realization. Due to the unique operation procedures and safety requirements of photochemical processes, existing technology from thermal processes cannot be easily modified for “retrofitting”. At present, a transfer of existing photochemical processes from the fragrance and flavor industry to solar-operated processes nevertheless appears realistic and technically feasible. In the long term, initial technology transfer costs will be compensated by annual savings on energy, cooling water, and especially replacement lamps. Tandem solar-lamp-driven processes furthermore offer “delivery security” for chemical manufacturing. During poor illumination conditions or at night, economical and energy efficient light sources such as light-emittion diodes (LEDs)28 or organic light-emitting diodes (OLEDs)179 can drive the photochemical conversion. A prototype solar-lamp device has recently been described for photocatalytic oxidation of ndecane.180 Solar-powered electrical components may likewise be incorporated into technical processes, thus further reducing electricity costs. Photovoltaic (PV) powered light sources have already been developed for point-of-use disinfection of drinking water.181 Solar photochemistry thus offers attractive business opportunities for sun-blessed developing countries, in particular for small-scale conversions of local biomass.182 In remote areas, PV panels can drive all remaining electrical components such as pumps or heat exchangers. Such “solar driven solar reactors” have been pioneered for water detoxification applications.183 A compact flow-through reactor module with solar-driven microwave discharge electrodeless lamps (MDLEs) and peristaltic pumps has likewise been developed by Horikoshi et al.184 The unit is designed for disaster relief and was successfully tested for the treatment of contaminated water.

transferred to the PROPHIS plant, the CPC module, and two simple flatbed reactors. The aperture of each reactor was set to 3 m2. Weather conditions varied during the 3-day campaign, and as a result, incomplete conversions were reached in all cases. Due to omitted degassing with an inert gas prior to exposure, all outdoor syntheses additionally generated large quantities of unknown byproducts. The PROPHIS facility produced a low conversion of approximately 40% after 19 h of operation, of which only 7% was determined to be 57. The CPC reactor showed satisfactory performance and reached a conversion of 53% and a 57 content of 17% after 17 h of solar exposure. The flatbed reactor pair achieved a conversion of just 30%, of which 3.6% was assigned to 57. Their static design proved especially problematic during the campaign with low temperatures during night times. Due to its importance in the fragrance industry,52,153 Oelgemöller et al.79 conducted the Schenck−ene reaction of citronellol (32) in five different solar reactors and under two different solar conditions at DLR in Germany (Figure 14;

Figure 14. Photooxygenation campaign in different solar reactors (DLR, Germany).

Scheme 24). During a sunny experimental phase, complete conversions were reached within 2.5−15 h of illumination, with the advanced PROPHIS facility showing the fastest performance. Due to its dependence on direct radiation, the PROPHIS plant was not operated under overcast conditions. In contrast, the CPC system and the flatbed performed satisfactorily and produced complete consumption after 30 h of operation. The unique design of the CPC reflector and the large exposed surface area of the flatbed were found advantageous for operations under diffuse solar conditions. Consequently, the CPC design is now widely found in solar chemistry.97,110,111 The simple horizontal and vertical tube reactors both gave incomplete conversions after 33 h of exposure. The solar synthesis campaign clearly demonstrated that nonconcentrating reactors systems can operate under a variety of sunlight conditions.

Scheme 24. Results for Solar Photooxygenation of Citronellol (32) in Five Different Reactors

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6. CONCLUDING REMARKS The examples presented in this review clearly demonstrate that sunlight is an attractive energy source for solar manufacturing of low-volume fine chemicals. Due to the low UV content of natural sunlight, target compounds are often obtained in high yields and purities. Solar concentrators are attractive tools to accelerate photochemical reactions with low quantum efficiencies; however, these devices require direct sunlight and create significant installation and operation costs. In comparison, nonto low-concentrating solar devices are economical and operate more robustly under poor weather conditions.79,150,172 Cost evaluations for the solar versus lamp-driven production of εcaprolactam (47)185,186 and rose oxide (34)187 have revealed that these important industrial chemicals can be manufactured economically in the long term. The environmental benefits of solar chemistry have also been recently confirmed by Ravelli et al.,188 using environmental assessment criteria, for the synthesis of rose oxide (34). Solar synthesis saw a boom in 1990−2005, when large research institutions such as PSA in Spain and DLR in Germany had dedicated research programs,189 but has since seen a decline. At the same time, new progress in solar technologies and visible-light driven photochemical processes has been achieved. It is hoped that the recognition of solar chemistry as a sustainable manufacturing methodology by funding agencies, private investors and industries will soon lead to a “new (solar) photochemistry of the future”. Ultimately, Ciamician’s prophetic warning “for nature is not in a hurry and mankind is” still stands today after over a century.75

past. Financial support came from the Irish Research Council for Science, Engineering and Technology (IRCSET; Ph.D. Scholarship 2006), the Irish Environmental Protection Agency (STRIVE; Ph.D. Scholarship 2007-PhD-ET-7), James Cook University (JCU Faculty Grants Schemes 2009 and 2011), the Australian Institute of Tropical Health and Medicine (AITHM; Development Grant 2012), and the Queensland Department of Employment, Economic Development & Innovation (DEEDI; Proof of Concept Grant 2012).

REFERENCES (1) Braslavsky, S. E. Glossary of Terms Used in Photochemistry. Pure Appl. Chem. 2007, 79, 293−465. (2) Bochet, C. G. Chromatic Orthogonality in Organic Synthesis. Synlett 2004, 2268−2274. (3) Pfoertner, K.-H.; Oppenländer, T. Photochemistry. In Ullmann’s Encyclopedia of Industrial Chemistry; Wiley−VCH: Weinheim, Germany, 2012; pp 1−45; DOI: 10.1002/14356007.a19_573.pub2. (4) Balzani, V.; Scandola, F. Chemistry and Light. Part 1: ́ Nova 1996, Photochemistry, A New Dimension of Chemistry. Quim. 19, 542−548. (5) Frackowiak, D. The Jablonski Diagram. J. Photochem. Photobiol., B 1988, 2, 399−408. (6) Brimioulle, R.; Lenhart, D.; Maturi, M. M.; Bach, T. Enantioselective Catalysis of Photochemical Reactions. Angew. Chem., Int. Ed. 2015, 54, 3872−3890. (7) Protti, S.; Fagnoni, M.; Ravelli, D. Photocatalytic C-H Activation by Hydrogen-Atom Transfer in Synthesis. ChemCatChem 2015, 7, 1516−1523. (8) Hoffmann, N. Electron and Hydrogen Transfer in Organic Photochemical Reactions. J. Phys. Org. Chem. 2015, 28, 121−136. (9) Hoffmann, N. Photochemical Reactions as Key Steps in Organic Synthesis. Chem. Rev. 2008, 108, 1052−1103. (10) Fagnoni, M.; Dondi, D.; Ravelli, D.; Albini, A. Photocatalysis for the Formation of the C-C Bond. Chem. Rev. 2007, 107, 2725−2756. (11) De Keukeleire, D.; He, S.-L. Photochemical Strategies for the Construction of Polycyclic Molecules. Chem. Rev. 1993, 93, 359−380. (12) Margaretha, P. Preparative Organic Photochemisty; Lehn, J.-M., Ed.; Topics in Current Chemistry, Vol. 103; Springer-Verlag: Berlin and Heidelberg, Germany, 1992; DOI: 10.1007/BFb0022836. (13) Bach, T.; Hehn, J. P. Photochemical Reactions as Key Steps in Natural Product Synthesis. Angew. Chem., Int. Ed. 2011, 50, 1000− 1045. (14) Iriondo-Alberdi, J.; Greaney, M. F. Photocycloaddition in Natural Product Synthesis. Eur. J. Org. Chem. 2007, 2007, 4801−4815. (15) Demuth, M. Synthesis of Natural Products Based on Photochemical Key Transformations. Pure Appl. Chem. 1986, 58, 1233−1238. (16) Oelgemö ller, M. Green Photochemical Processes and Technologies for Research & Development, Scale-up and Chemical Production. J. Chin. Chem. Soc. 2014, 61, 743−748. (17) Hoffmann, N. Homogeneous Photocatalytic Reactions with Organometallic and Coordination Compounds - Perspectives for Sustainable Chemistry. ChemSusChem 2012, 5, 352−371. (18) Hoffmann, N. Photochemical Reactions of Aromatic Compounds and the Concept of the Photon as a Traceless Reagent. Photochem. Photobiol. Sci. 2012, 11, 1613−1641. (19) Ciana, C. L.; Bochet, C. G. Clean and Easy Photochemistry. Chimia 2007, 61, 650−654. (20) Albini, A.; Fagnoni, M.; Mella, M. Environment-Friendly Organic Synthesis. The Photochemical Approach. Pure Appl. Chem. 2000, 72, 1321−1326. (21) Braun, A. M.; Maurette, M.; Oliveros, E. Photochemical Technology; Wiley: Chichester, U.K., 1991. (22) Andre, J.-C.; Vannes, A.-B. Techniques d’Utilisation des Photons; Dopee85: Avon, France, 1992. (23) van den Hoek, W. J.; Luijks, G. M. J. F., Hoelen, C. G. H. Lamps. In Ullmann’s Encyclopedia of Industrial Chemistry; Wiley−VCH:

AUTHOR INFORMATION Corresponding Author

*E-mail [email protected]. Notes

The author declares no competing financial interest. Biography Associate Professor Michael Oelgemöller received his diploma from the University of Münster in 1995 and his Ph.D. from the University of Cologne in 1999. He was a researcher at the ERATO−JST Photochirogenesis project in Osaka (1999−2001) and at Bayer CropScience K.K. Japan in Yuki (2001−2004). From 2004 to 2008 he held a position as a lecturer in organic and medicinal chemistry at Dublin City University. In February 2009 he joined James Cook University in Townsville as an associate professor in organic chemistry, where he leads the Applied and Green Photochemistry Research Group.190 Activities of the group range from development of continuous-flow photoreactors to solar manufacturing of chemicals, photochemical synthesis of bioactive compounds, photostability testing, and photochemical degradation of organic pollutants. He has received several awards and has been a visiting professor at various universities in Asia and Europe.

ACKNOWLEDGMENTS I thank Dr. Peter Esser, Dr. Achim Hülsdünker, Dr. Christian Jung, Dr. Christian Sattler, and Dr. Karl-Heinz Funken for valuable information and resources, and Dr. Marie M'Balla-Ndi for help in the preparation of this manuscript. I also thank my diploma mentor emeritus Professor Jochen Mattay (University of Bielefeld), our collaborators, and all students who have contributed to the success of our solar research projects in the 9678


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Chemistry Synthesis of Substituted Cyclopropanes. Photochem. Photobiol. Sci. 2012, 11, 1929−1937. (46) Luis, P.; Van der Bruggen, B. Exergy Analysis of EnergyIntensive Production Processes: Advancing Towards a Sustainable Chemical Industry. J. Chem. Technol. Biotechnol. 2014, 89, 1288−1303. (47) Neelis, M.; Patel, M.; Bach, P.; Blok, K. Analysis of Energy Use and Carbon Losses in the Chemical Industry. Appl. Energy 2007, 84, 853−862. (48) Patel, M. Cumulative Energy Demand (CED) and Cumulative CO2 Emissions for Products of the Organic Chemical Industry. Energy 2003, 28, 721−740. (49) Haggiage, E.; Coyle, E. E.; Joyce, K.; Oelgemöller, M. Green Photochemistry: Solarchemical Synthesis of 5-Amido-1,4-naphthoquinones. Green Chem. 2009, 11, 318−321. (50) Protti, S.; Ravelli, D.; Fagnoni, M.; Albini, A. Solar Light-Driven Photocatalyzed Alkylations. Chemistry on the Window Ledge. Chem. Commun. 2009, 7351−7353. (51) Fischer, M. Industrial Applications of Photochemical Syntheses. Angew. Chem., Int. Ed. Engl. 1978, 17, 16−26. (52) Gollnick, K. Photooxygenation and its Application in Industry. Chim. Ind. 1982, 64, 156−166. (53) Wilkins, F. W.; Blake, D. M. Use Solar Energy to Drive Chemical Processes. Chem. Eng. Prog. 1994, 90, 41−49. (54) Balzani, V.; Credi, A.; Venturi, M. Photochemical Conversion of Solar Energy. ChemSusChem 2008, 1, 26−58. (55) Stankiewicz, A. Energy Matters. Alternative Sources and Forms of Energy for Intensification of Chemical and Biochemical Processes. Chem. Eng. Res. Des. 2006, 84, 511−521. (56) Bolton, J. R.; Hall, D. O. Photochemical Conversion and Storage of Solar Energy. Annu. Rev. Energy 1979, 4, 353−401. (57) Luther, J.; Nast, M.; Fisch, M. N.; Christoffers, D.; Pfisterer, F.; Meissner, D.; Nitsch, J.; Becker, M. Solar Technology. In Ullmann’s Encyclopedia of Industrial Chemistry; Wiley−VCH: Weinheim, Germany, 2012; pp 1−58; DOI: 10.1002/14356007.a24_369.pub2. (58) Fu, Q. Radiation (Solar). In Encyclopedia of Atmospheric Sciences; Holton, J., Ed.; Academic Press: Amsterdam, The Netherlands, 2003; pp 1859−1863; DOI: 10.1016/B0-12-227090-8/00334-1. (59) Bahnemann, D. Photocatalytic Water Treatment: Solar Energy Applications. Sol. Energy 2004, 77, 445−459. (60) Schlögl, R. The Role of Chemistry in the Energy Challenge. ChemSusChem 2010, 3, 209−222. (61) Worrell, E.; van Berkel, R.; Fengqi, Z.; Menke, C.; Schaeffer, R.; Williams, R. O. Technology Transfer of Energy Efficient Technologies in Industry: A Review of Trends and Policy Issues. Energy Policy 2001, 29, 29−43. (62) Roth, H. D. The Beginnings of Organic Photochemistry. Angew. Chem., Int. Ed. Engl. 1989, 28, 1193−1207. (63) Roth, H. D. Twentieth Century Developments in Photochemistry. Brief Historical Sketches. Pure Appl. Chem. 2001, 73, 395− 403. (64) Klinger, H. Ueber das Isobenzil und die Einwirkung des Sonnenlichts auf einige Organische Substanzen. Ber. Dtsch. Chem. Ges. 1886, 19, 1862−1870. (65) Klinger, H. Ueber die Einwirkung des Sonnenlichts auf Organische Verbindungen. Justus Liebigs Ann. Chem. 1888, 249, 137−146. (66) Roth, H. D. A Tribute to Stanislao Cannizzaro, Chemical Informationist and Photochemist. Photochem. Photobiol. Sci. 2011, 10, 1849−1853. (67) Rubin, M. B. Pioneers in Photochemistry: Emanuele Paternò, 1847−1935. Eur. Photochem. Assoc. Newsl. 1982, 15 (June), 4−7. (68) Heindel, N. D.; Pfau, M. A. A Profitable Partnership. Giacomo Ciamician and Paul Silber. J. Chem. Educ. 1965, 42, 383−386. (69) Albini, A.; Dichiarante, V. The Belle Époque of Photochemistry. Photochem. Photobiol. Sci. 2009, 8, 248−254. (70) Ciamician, G. Actions Chimiques de la Lumière. Bull. Soc. Chim. Fr. 1908, 3−4, I−xxvii. (71) Ciamician, G.; Silber, P. Chemische Lichtwirkungen. Ber. Dtsch. Chem. Ges. 1900, 33, 2911−2913.

Weinheim, Germany, 2012; pp 237−288; DOI: 10.1002/ 14356007.a15_115.pub3. (24) Parnis, J. M.; Oldham, K. B. Beyond the Beer−Lambert Law: the Dependence of Absorbance on Time in Photochemistry. J. Photochem. Photobiol., A 2013, 267, 6−10. (25) Rubin, M. B.; Braslavsky, S. E. Quantum Yield: the Term and the Symbol. A Historical Search. Photochem. Photobiol. Sci. 2010, 9, 670−674. (26) Wilson, R. M.; Schnapp, K. A. High-Intensity Laser Photochemistry of Organic Molecules in Solution. Chem. Rev. 1993, 93, 223−249. (27) Sosnin, E. A.; Oppenländer, T.; Tarasenko, V. F. Applications of Capacitive and Barrier Discharge Excilamps in Photoscience. J. Photochem. Photobiol., C 2006, 7, 145−163. (28) Griesbeck, A. G.; Maptue, N.; Bondock, S.; Oelgemöller, M. The Excimer Radiation System: A Powerful Tool for Preparative Organic Photochemistry. A Technical Note. Photochem. Photobiol. Sci. 2003, 2, 450−451. (29) Landgraf, S. Application of Semiconductor Light Sources for Investigations of Photochemical Reactions. Spectrochim. Acta, Part A 2001, 57, 2029−2048. (30) Jo, W.-K.; Tayade, R. J. New Generation Energy-Efficient Light Source for Photocatalysis: LEDs for Environmental Applications. Ind. Eng. Chem. Res. 2014, 53, 2073−2084. (31) Pinho, V. D.; Miranda, L. S. M.; de Souza, R. O. M. A. Photochemistry Under Continuous Flow Conditions. Rev. Virtual Quim. 2015, 7, 144−164. (32) Gilmore, K.; Seeberger, P. H. Continuous Flow Photochemistry. Chem. Rec. 2014, 14, 410−416. (33) Oelgemöller, M. Highlights of Photochemical Reactions in Microflow Reactors. Chem. Eng. Technol. 2012, 35, 1144−1152. (34) Oelgemöller, M.; Shvydkiv, O. Recent Advances in Microflow Photochemistry. Molecules 2011, 16, 7522−7550. (35) Coyle, E. E.; Oelgemöller, M. Micro-photochemistry: Photochemistry in Microstructured Reactors. The New Photochemistry of the Future? Photochem. Photobiol. Sci. 2008, 7, 1313−1322. (36) Matsushita, Y.; Ichimura, T.; Ohba, N.; Kumada, S.; Sakeda, K.; Suzuki, T.; Tanibata, H.; Murata, T. Recent Progress on Photoreactions in Microreactors. Pure Appl. Chem. 2007, 79, 1959−1968. (37) Martín-Flesia, M.; Postigo, A. Photoinduced Cyclization Reactions in Aqueous Media. Curr. Org. Chem. 2012, 16, 2379−2388. (38) Griesbeck, A. G.; Kramer, W.; Oelgemöller, M. Photoinduced Decarboxylation Reactions. Radical Chemistry in Water. Green Chem. 1999, 1, 205−207. (39) Hernández-Linares, M. G.; Guerrero-Luna, G.; Pérez-Estrada, S.; Ellison, M.; Ortin, M.-M.; Garcia-Garibay, M. A. Large-Scale Green Chemical Synthesis of Adjacent Quaternary Chiral Centers by Continuous Flow Photodecarbonylation of Aqueous Suspensions of Nanocrystalline Ketones. J. Am. Chem. Soc. 2015, 137, 1679−1684. (40) Turro, N. J.; Grätzel, M.; Braun, A. M. Photophysical and Photochemical Processes in Micellar Systems. Angew. Chem., Int. Ed. Engl. 1980, 19, 675−696. (41) Pagni, R. M. Recent Developments in Photochemistry in Ionic Liquids. Chim. Oggi 2007, 25, 28−31. (42) Tanko, J. M.; Blackert, J. F.; Sadeghipour, M. Supercritical Carbon Dioxide as a Medium for Conducting Free-Radical Reactions. In Benign by Design: Alternative Synthetic Design for Pollution Prevention; Anastas, P. T., Farris, C. A., Eds.; ACS Symposium Series, Vol. 577; American Chemical Society: Washington, DC, 1994; Chapt. 8, pp 98− 113; DOI: 10.1021/bk-1994-0577.ch008. (43) Griesbeck, A. G.; Kramer, W.; Oelgemöller, M. Synthetic Applications of Photoinduced Electron Transfer Decarboxylation Reactions. Synlett 1999, 1999, 1169−1178. (44) Budac, D.; Wan, P. Photodecarboxylation: Mechanism and Synthetic Utility. J. Photochem. Photobiol., A 1992, 67, 135−166. (45) Shiraki, S.; Vogelsberg, C. S.; Garcia-Garibay, M. A. Solid-State Photochemistry of Crystalline Pyrazolines: Reliable Generation and Reactivity Control of 1,3-Biradicals and their Potential for the Green 9679


Chemical Reviews

Review

(72) Ciamician, G.; Silber, P. Chemische Lichtwirkungen. XIII. Mitteilung. Ber. Dtsch. Chem. Ges. 1908, 41, 1928−1935. (73) Büchi, G.; Goldman, I. M. Photochemical Reactions. VII. The Intramolecular Cyclization of Carvone to Carvonecamphor. J. Am. Chem. Soc. 1957, 79, 4741−4748. (74) Meinwald, J.; Schneider, R. A. Photochemical Synthesis and Reactions of Carvonecamphor. J. Am. Chem. Soc. 1965, 87, 5218− 5229. (75) Ciamician, G. The Photochemistry of the Future. Science 1912, 36, 385−394. (76) Protti, S.; Fagnoni, M. The Sunny Side of Chemistry: Green Synthesis by Solar Light. Photochem. Photobiol. Sci. 2009, 8, 1499− 1516. (77) Spasiano, D.; Marotta, R.; Malato, S.; Fernandez-Ibañez, P.; Di Somma, I. Solar Photocatalysis: Materials, Reactors, some Commercial, and pre-Industrialized Applications. A Comprehensive Approach. Appl. Catal., B 2015, 170-171, 90−123. (78) Mumtaz, S.; Sattler, C.; Oelgemöller, M. Solar Photochemical Manufacturing of Fine Chemicals − Historical Background, Modern Solar Technologies, Recent Applications and Future Challenges. In Chemical Processes for a Sustainable Future; Letcher, T. M., Scott, J. L., Patterson, D., Eds.; Royal Society of Chemistry: Cambridge, U.K., 2015, Chapt. 7; pp 158−191. (79) Oelgemöller, M.; Jung, C.; Mattay, J. Green Photochemistry: Production of Fine Chemicals with Sunlight. Pure Appl. Chem. 2007, 79, 1939−1947. (80) Oelgemöller, M.; Jung, C.; Ortner, J.; Mattay, J.; Schiel, C.; Zimmermann, E. Green Photochemistry with Moderately Concentrated Sunlight. Spectrum (Bowling Green, OH, U. S.) 2005, 18 (1), 28− 33. (81) Esser, P.; Pohlmann, B.; Scharf, H.-D. The Photochemical Synthesis of Fine Chemicals with Sunlight. Angew. Chem., Int. Ed. Engl. 1994, 33, 2009−2023. (82) Pohlmann, B.; Scharf, H.-D.; Jarolimek, U.; Mauermann, P. Photochemical Production of Fine Chemicals with Concentrated Sunlight. Sol. Energy 1997, 61, 159−168. (83) Funken, K.-H. Solare Photoreaktionen für die Chemische Technik. Nachr. Chem., Tech. Lab. 1992, 40, 793−800. (84) Schultz, D. M.; Yoon, T. P. Solar Synthesis: Prospects in Visible Light Photocatalysis. Science 2014, 343, 1239176. (85) Angnes, R. A.; Li, Z.; Correia, C. R. D.; Hammond, G. B. Recent Synthetic Additions to the Visible Light Photoredox Catalysis Toolbox. Org. Biomol. Chem. 2015, 13, 9152−9167. (86) Tan, F.; Xiao, W. Visible-Light Photoredox Catalysis in Natural Products Synthesis. Huaxue Xuebao 2015, 73, 85−89. (87) Koike, T.; Akita, M. Visible-Light-Induced Redox Reactions by Ruthenium Photoredox Catalyst. Top. Organomet. Chem. 2014, 48, 371−396. (88) Koike, T.; Akita, M. Visible-Light-Induced Photoredox Catalysis: An Easy Access to Green Radical Chemistry. Synlett 2013, 24, 2492−2505. (89) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C. Visible Light Photoredox Catalysis with Transition Metal Complexes: Applications in Organic Synthesis. Chem. Rev. 2013, 113, 5322−5363. (90) Kalogirou, S. A. Solar Thermal Collectors and Applications. Prog. Energy Combust. Sci. 2004, 30, 231−295. (91) Fernández-García, A.; Zarza, E.; Valenzuela, L.; Pérez, M. Parabolic-Trough Solar Collectors and Their Applications. Renewable Sustainable Energy Rev. 2010, 14, 1695−1721. (92) Roeb, M.; Neises, M.; Monnerie, N.; Sattler, C.; Pitz-Paal, R. Technologies and Trends in Solar Power and Fuels. Energy Environ. Sci. 2011, 4, 2503−2511. (93) Mills, D. Advances in Solar Thermal Electricity Technology. Sol. Energy 2004, 76, 19−31. (94) Weinstein, L. A.; Loomis, J.; Bhatia, B.; Bierman, D. M.; Wang, E. N.; Chen, G. Concentrating Solar Power. Chem. Rev. 2015, 115, 12797−12838.

(95) Malato, S.; Blanco, J.; Vidal, A.; Richter, C. Photocatalysis with Solar Energy at a Pilot-Plant Scale: An Overview. Appl. Catal., B 2002, 37, 1−15. (96) Funken, K.-H.; Ortner, J. Technologies for the Solar Photochemical and Photocatalytic Manufacture of Specialities and Commodities: a Review. Z. Phys. Chem. 1999, 213, 99−105. (97) Malato, S.; Blanco, J.; Richter, C.; Curcó, D.; Giménez, J. LowConcentrating CPC Collectors for Photocatalytic Water Detoxification. Comparison with a Medium Concentrating Solar Collector. Water Sci. Technol. 1997, 35, 157−164. (98) Becker, M.; Meinecke, W.; Sattler, C. Konzentrierende Solarsysteme und Solare Chemie. BWK: Energie-Fachmagazin 2000, 52, 72−76. (99) Richter, C.; Martinez, D. Plataforma Solar de Almerı ́a. Eine Deutsch-Spanische Zusammenarbeit. DLR Nachr. 2005, 109, 22−27. (100) Funken, K.-H.; Becker, M. Solar Chemical Engineering and Solar Materials Research into the 21st Century. Renewable Energy 2001, 24, 469−474. (101) Iqbal, M. An Introduction to Solar Radiation; Academic Press: New York, 1983. (102) Schenck, G. O.; Schulze-Buschoff, H. Synthetisches Askaridol, eine Neue Mö glichkeit der Spulwurmbehandlung. Dtsch. Med. Wochenschr. 1948, 73, 341−345. (103) Schenck, G. O.; Kinkel, K. G.; Mertens, H.-J. Photochemsiche Reaktionen I. Ü ber die Photosynthese des Askaridols und Verwandter Endoperoxyde. Justus Liebigs Annal. Chem. 1953, 584, 125−155. (104) Ronzani, F.; Costarramone, N.; Blanc, S.; Benabbou, A. K.; LeBechec, M.; Pigot, T.; Oelgemöller, M.; Lacombe, S. Visible-light Photosensitized Oxidation of α-Terpinene Using Novel SilicaSupported Sensitizers: Photooxygenation vs. Photodehydrogenation. J. Catal. 2013, 303, 164−174. (105) Lévesque, F.; Seeberger, P. H. Highly Efficient Continuous Flow Reactions Using Singlet Oxygen as a Green Reagent. Org. Lett. 2011, 13, 5008−5011. (106) Zhao, Y. P.; Campbell, R. O.; Liu, R. S. H. Solar Reactions for Preparing Hindered 7-cis-Isomers of Dienes and Trienes in the Vitamin A Series. Green Chem. 2008, 10, 1038−1042. (107) Guillet, J. E.; Sherren, J.; Gharapetian, H. M.; MacInnis, W. K. Prospects for Solar Synthesis I: A New Method for Singlet Oxygen Reactions using Natural Sunlight. J. Photochem. 1984, 25, 501−509. (108) Ajona, J. I.; Vidal, A. The Use of CPC Collectors for Detoxification of Contaminated Water: Design, Construction and Preliminary Results. Sol. Energy 2000, 68, 109−120. (109) Tanveer, M.; Guyer, G. T. Solar Assisted Photo Degradation of Wastewater by Compound Parabolic Collectors: Review of Design and Operation Parameters. Renewable Sustainable Energy Rev. 2013, 24, 534−543. (110) Blanco, J.; Malato, S.; Fernández, P.; Vidal, A.; Morales, A.; Trincado, P.; Oliveria, J. C.; Minero, C.; Musci, M.; Casalle, C.; et al. Compound Parabolic Concentrator Technology Development to Commercial Solar Detoxification Applications. Sol. Energy 1999, 67, 317−330. (111) Fernández, P.; Blanco, J.; Sichel, C.; Malato, S. Water Disinfection by Solar Photocatalysis Using Compound Parabolic Collectors. Catal. Today 2005, 101, 345−352. (112) Oelgemöller, M. The Sunny Side of Chemistry at James Cook Uni. Chem. Aust. 2014, November, 7−9. (113) Fernández-García, A.; Zarza, E.; Valenzuela, L.; Pérez, M. Parabolic-Trough Solar Collectors and their Applications. Renewable Sustainable Energy Rev. 2010, 14, 1695−1721. (114) Jung, C.; Funken, K. H.; Ortner, J. PROPHIS: Parabolic Trough-Facility for Organic Photochemical Syntheses in Sunlight. Photochem. Photobiol. Sci. 2005, 4, 409−411. (115) Dunn, R.; Lovegrove, K.; Burgess, G. A Review of AmmoniaBased Thermochemical Energy Storage for Concentrating Solar Power. Proc. IEEE 2012, 100, 391−400. (116) Alp, S.; Ertekin, K.; Horn, M.; Icli, S. Photostability Studies of Thermomesomorphic Derivatives of 2,5-Dihydropyrrolo[3,4-c]pyrrole-1,4-dione. Dyes Pigm. 2004, 60, 103−110. 9680


Chemical Reviews

Review

(140) Kim, Y. J.; Jeong, M. J.; Kim, J. E.; In, I.; Park, C. P. Microreactor-Mediated Benzylic Bromination in Concentrated Solar Radiation. Aust. J. Chem. 2015, 68, 1653−1656. (141) Nsubuga, H.; Basheer, C.; Al-Muallem, H. A. S.; Kalanthoden, A. N. Isolation, Characterization and Evaluation of Photochemical Potential of Rice Husk-Based Furfural via Continuous Flow Reactor. J. Environ. Chem. Eng. 2016, 4, 857−863. (142) Zhao, Y.-P.; Yang, L.-Y.; Liu, R. S. H. Designing Systems for One-way trans to cis Photoisomerization for Solar Reactions. Green Chem. 2009, 11, 837−842. (143) Spasiano, D.; del Pilar Prieto Rodriguez, L.; Olleros, J. C.; Malato, S.; Marotta, R.; Andreozzi, R. TiO2/Cu(II) Photocatalytic Production of Benzaldehyde from Benzyl Alcohol in Solar Pilot Plant Reactor. Appl. Catal., B 2013, 136−137, 56−63. (144) Bolte, M.; Klaeden, K.; Beqiraj, A.; Oelgemö ller, M. Photochemistry Down Under − Solar Chemicals from and for the Tropics. Eur. Photochem. Assoc. Newsl. 2013, 84, 79−83. (145) Schweitzer, C.; Schmidt, R. Physical Mechanisms of Generation and Deactivation of Singlet Oxygen. Chem. Rev. 2003, 103, 1685−1757. (146) Wahlen, J.; De Vos, D. E.; Jacobs, P. A.; Alsters, P. L. Solid Materials as Sources for Synthetically Useful Singlet Oxygen. Adv. Synth. Catal. 2004, 346, 152−164. (147) Ronzani, F.; Saint-Cricq, P.; Arzoumanian, E.; Pigot, T.; Blanc, S.; Oelgemö ller, M.; Oliveros, E.; Richard, C.; Lacombe, S. Immobilized Organic Photosensitizers with Versatile Reactivity for Various Visible-Light Applications. Photochem. Photobiol. 2014, 90, 358−368. (148) Oelgemöller, M.; Mattay, J. The “Photochemical Friedel-Crafts Acylation” of Quinones: From the Beginnings of Organic Photochemistry to Modern Solar Chemical Applications. In CRC Handbook of Organic Photochemistry and Photobiology. 2nd ed.; Horspool, W. M., Lenci, F., Eds.; CRC Press, Taylor & Francis Group: Boca Raton, FL, 2004; Vol. 2, Chapt. 88, pp 1−45. (149) Schiel, C.; Oelgemöller, M.; Mattay, J. Photoacylation of Electron-Rich Quinones: An Application of the Photo-Friedel-Crafts Reaction. Synthesis 2001, 112 (8), 1275−1279. (150) Schiel, C.; Oelgemöller, M.; Ortner, J.; Mattay, J. Green Photochemistry: The Solar-Chemical Photo-Friedel-Crafts Acylation of Quinones. Green Chem. 2001, 3, 224−228. (151) Oelgemöller, M.; Schiel, C.; Fröhlich, R.; Mattay, J. The PhotoFriedel-Crafts Acylation of 1,4-Naphthoquinones. Eur. J. Org. Chem. 2002, 2002, 2465−2474. (152) Oelgemöller, M.; Jung, C.; Ortner, J.; Mattay, J.; Zimmermann, E. Green Photochemistry: Solar Photooxygenations with Medium Concentrated Sunlight. Green Chem. 2005, 7, 35−38. (153) Rojahn, W.; Warnecke, H.-U. Die Photosensibilisierte Sauerstoffübertragung - eine Methode zur Herstellung Hochwertiger Riechstoffe. Dragoco Rep. (Ger. Ed.) 1980, 27, 159−164. (154) Heller, B.; Heller, D.; Klein, H.; Richter, C.; Fischer, C.; Oehme, G. Progress in the Photocatalysed Synthesis of Pyridines. J. Inf. Rec. 2000, 25, 15−23. (155) Heller, B.; Heller, D.; Oehme, G. The Light Promoted Co1 Catalysed Synthesis of Substituted Pyridines. Eur. Photochem. Assoc. Newsl. 1998, 62, 37−50. (156) Oehme, G.; Heller, B.; Wagler, P. A Solar-driven, Complex Catalyzed Pyridine Synthesis as Alternative for a Thermally-Driven Synthesis. Energy 1997, 22, 327−336. (157) Heller, B.; Wagner, P.; Oehme, G. Co(I)-catalysed Pyridine Synthesis in Water. J. Inf. Rec. 1996, 22, 443−445. (158) Wagler, P.; Heller, B.; Ortner, J.; Funken, K.-H.; Oehme, G. Solare Photokatalytische Cocyclisierung von Acetylen und Nitrilen in Wasser. Chem. Ing. Tech. 1996, 68, 823−826. (159) Ritter, A.; Hülsdünker, A.; Ritterkamp, P.; Heimann, F.; Binder, W.; Klinge, S.; Demuth, M. Solare Photochemische Synthese von Feinchemikalien und Solartechnische Entwicklungen. In Solare Chemie und solare Materialforschung; Becker, M., Funken, K.-H., Eds.; Verlag C. F. Müller: Heidelberg, Germany, 1997; pp 204−216.

(117) Neumann, A.; Groer, U. Experimenting with Concentrated Sunlight using the DLR Solar Furnace. Sol. Energy 1996, 58, 181−190. (118) Chibante, L. P. F.; Thess, A.; Alford, J. M.; Diener, M. D.; Smalley, R. E. Solar Generation of the Fullerenes. J. Phys. Chem. 1993, 97, 8696−8700. (119) Fields, C. L.; Pitts, J. R.; Hale, M. J.; Bingham, C.; Lewandowski, A.; King, D. E. Formation of Fullerenes in Highly Concentrated Solar Flux. J. Phys. Chem. 1993, 97, 8701−8702. (120) Flamant, G.; Luxembourg, D.; Robert, J. F.; Laplaze, D. Optimizing Fullerene Synthesis in a 50 kW Solar Reactor. Sol. Energy 2004, 77, 73−80. (121) Guillard, T.; Flamant, G.; Robert, J.-F.; Rivoire, B.; Giral, J.; Laplaze, D. Scale up of a Solar Reactor for Fullerene and Nanotube Synthesis. J. Sol. Energy Eng. 2002, 124, 22−27. (122) Beach, E. S.; Cui, Z.; Anastas, P. T. Green Chemistry: A Design Framework for Sustainability. Energy Environ. Sci. 2009, 2, 1038−1049. (123) Watson, W. J. W. How do the Fine Chemical, Pharmaceutical, and Related Industries Approach Green Chemistry and Sustainability? Green Chem. 2012, 14, 251−259. (124) Tirronen, E.; Salmi, T. Process Development in the Fine Chemical Industry. Chem. Eng. J. 2003, 91, 103−114. (125) Obenndip, D. A.; Sharratt, P. N. Enhancing Fine Chemicals Process Chemistry. A Practical Approach. Chem. Eng. Res. Des. 2005, 83, 655−661. (126) Bruggink, A. Growth and Efficiency in the (Fine) Chemical Industry. Chim. Oggi 1998, 16, 44−47. (127) Funken, K.-H. Solar Chemistry: Classification, Criteria, and Identification of R & D Deficits. Sol. Energy Mater. 1991, 24, 370−385. (128) Dinda, M.; Maiti, S.; Samanta, S.; Ghosh, P. K. Illustration of Efficient Solar Driven Organic Reactions. Curr. Org. Synth. 2016, 13, 372−384. (129) Dinda, M.; Samanta, S.; Eringathodi, S.; Ghosh, P. K. Solar Photo-thermochemical Syntheses of 4-Bromo-2,5-substituted Oxazoles from N-Arylethylamides. RSC Adv. 2014, 4, 12252−12256. (130) Agee, B. M.; Mullins, G.; Swartling, D. J. Friedel-Crafts Acylation Using Solar Irradiation. ACS Sustainable Chem. Eng. 2013, 1, 1580−1583. (131) Deshpande, S.; Gadilohar, B.; Shinde, Y.; Pinjari, D.; Pandit, A.; Shankarling, G. Energy Efficient, Clean and Solvent Free Photochemical Benzylic Bromination Using NBS in Concentrated Solar Radiation (CSR). Sol. Energy 2015, 113, 332−339. (132) Dondi, D.; Protti, S.; Albini, A.; Carpio, S. M.; Fagnoni, M. Synthesis of γ-Lactols, γ-Lactones and 1,4-Monoprotected Succinaldehydes under Moderately Concentrated Sunlight. Green Chem. 2009, 11, 1653−1659. (133) Heller, B.; Klein, H.; Richter, C.; Wagler, P.; Fischer, C.; Oehme, G. Photocatalytic Synthesis of Substituted Pyridines. In Training and Mobility of Researchers Programme at Plataforma Solar de Almerı ́a, Proceedings of the 2nd Users Workshop, Almerı ́a, Spain, November 10−11, 1998; CIEMAT: Madrid, Spain, 2004; pp 119− 124. (134) Heller, B. Pyridinsynthese: Photokatalytisch und in Wasser. Nachr. Chem., Tech. Lab. 1999, 47, 9−14. (135) Covell, C.; Gilbert, A.; Richter, C. Sunlight-Induced Regio- and Stereo-Specific (2π + 2π) Cycloaddition of Arylethenes to 2Substituted-1,4-naphthoquinones. J. Chem. Res., Synop. 1998, 316− 317. (136) Hoffmann, M. R.; Martin, S. T.; Choi, W.; Bahnemann, D. W. Environmental Applications of Semiconductor Photocatalysis. Chem. Rev. 1995, 95, 69−96. (137) Kanakaraju, D.; Glass, B. D.; Oelgemöller, M. Titanium Dioxide Photocatalysis for Pharmaceutical Wastewater Treatment. Environ. Chem. Lett. 2014, 12, 27−47. (138) Hoffmann, N. Photocatalysis with TiO2 Applied to Organic Synthesis. Aust. J. Chem. 2015, 68, 1621−1639. (139) Cermenati, L.; Richter, C.; Albini, A. Solar Light Induced Carbon-Carbon Bond Formation via TiO2 Photocatalysis. Chem. Commun. 1998, 805−806. 9681


Chemical Reviews

Review

(160) Hülsdünker, A.; Ritter, A.; Demuth, M. Linearly Focussing Solar Reactor for Chemical Purpose. Eur. Photochem. Assoc. Newsl. 1992, 45, 23−25. (161) Oelgemöller, M.; Healy, N.; de Oliveira, L.; Jung, C.; Mattay, J. Green Photochemistry: Solar-chemical Synthesis of Juglone with Medium Concentrated Sunlight. Green Chem. 2006, 8, 831−834. (162) Ortner, J.; Faust, D.; Funken, K.-H.; Lindner, T.; Schulat, J.; Stojanoff, C. G.; Fröning, P. New Developments Using Holographic Concentration in Solar Photochemical Reactors. J. Phys. IV 1999, 9 (Pr3), 379−383. (163) Hull, J.; Lauer, J.; Broadbent, D. Holographic Solar Concentrators. Energy 1987, 12, 209−215. (164) Suchard, O.; Kane, R.; Roe, B. J.; Zimmermann, E.; Jung, C.; Waske, P. A.; Mattay, J.; Oelgemöller, M. Photooxygenations of 1Naphthols: An Environmentally Friendly Access to 1,4-Naphthoquinones. Tetrahedron 2006, 62, 1467−1473. (165) Ngoh, S. K.; Njomo, D. An Overview of Hydrogen Gas Production from Solar Energy. Renewable Sustainable Energy Rev. 2012, 16, 6782−6792. (166) Steinfeld, A. Solar Thermochemical Production of Hydrogen A Review. Sol. Energy 2005, 78, 603−615. (167) Avcibaşi, N.; Içli, S.; Gilbert, A. Photochemical Reactions of αTerpinene and Acenaphthene Under Concentrated Sunlight. Turk. J. Chem. 2003, 27, 1−7. (168) Içli, S.; Bulut, A.; Gül, Y. Room Temperature Generation of Dehydrogenated Colophony: Solar Chemical Production. Turk. J. Chem. 1992, 16, 289−292. (169) Funken, K.-H.; Luedtke, G.; Ortner, J.; Riffelmann, K.-J. Solar Photochemical Production of ε-Caprolactam Using Highly Concentrated Sunlight. J. Inf. Rec 2000, 25, 3−14. (170) Talukdar, J.; Wong, E. H. S.; Mathur, V. K. Caprolactam Production by Direct Solar Flux. Sol. Energy 1991, 47, 165−171. (171) Jung, C.; Ortner, J.; Jarolimek, U.; Mauermann, P.; Leyen, B. Advances in Photochemical Production of Fine Chemicals with Concentrated Sunlight. In Solare Chemie und solare Materialforschung [CD-ROM]; AG-Solar NRW: Wuppertal, Germany, 2002; Chapt. 2.2, pp 1−10. (172) Heinemann, C.; Xing, X.; Warzecha, K. D.; Ritterskamp, P.; Görner, H.; Demuth, M. An Asymmetric Induction Principle and Biomimetics with Photons via Electron Transfer. Pure Appl. Chem. 1998, 70, 2167−2176. (173) Oelgemöller, M.; Mattay, J.; Jung, C.; Schiel, C.; Ortner, C.; Zimmermann, E. Back to the Roofs − The Solarchemical Production of Fine Chemicals with Sunlight. In Proceedings of the ASME 2004 International Solar Energy Conference, Portland, OR, July 11−14, 2004; American Society of Mechanical Engineers: New York, 2004; Article ISEC2004-65021, pp 523−531; DOI: 10.1115/ISEC200465021. (174) Mattay, J. Von der Laborsynthese zur Solarchemie. Chem. Unserer Zeit 2002, 36, 98−106. (175) Anastas, P.; Eghbali, N. Green Chemistry: Principles and Practice. Chem. Soc. Rev. 2010, 39, 301−312. (176) Jiménez-González, C.; Constable, D. J. C.; Ponder, C. S. Evaluating the Greenness of Chemical Processes and Products in the Pharmaceutical Industry − A Green Metrics Primer. Chem. Soc. Rev. 2012, 41, 1485−1498. (177) Böschen, S.; Lenoir, D.; Scheringer, M. Sustainable Chemistry: Starting Points and Prospects. Naturwissenschaften 2003, 90, 93−102. (178) Ravelli, D.; Protti, S.; Fagnoni, M.; Albini, A. Visible Light Photocatalysis. A Green Choice? Curr. Org. Chem. 2013, 17, 2366− 2373. (179) Kalyani, N. T.; Dhoble, S. J. Organic Light Emitting Diodes: Energy Saving Lighting Technology − A Review. Renewable Sustainable Energy Rev. 2012, 16, 2696−2723. (180) Monteiro, R. A. R.; Rodrigues-Silva, C.; Lopes, F. V. S.; Silva, A. M. T.; Boaventura, R. A. R.; Vilar, V. J. P. Evaluation of a Solar/UV Annular Pilot Scale Reactor for 24 h Continuous Photocatalytic Oxidation of n-Decane. Chem. Eng. J. 2015, 280, 409−416.

(181) Lui, G. Y.; Roser, D.; Corkish, R.; Ashbolt, N.; Jagals, P.; Stuetz, R. Photovoltaic Powered Ultraviolet and Visible Light-Emitting Diodes for Sustainable Point-of-use Disinfection of Drinking Water. Sci. Total Environ. 2014, 493, 185−196. (182) Gallezot, P. Conversion of Biomass to Selected Chemical Products. Chem. Soc. Rev. 2012, 41, 1538−1558. (183) Navntoft, C.; Araujo, P.; Litter, M. I.; Apella, M. C.; Fernández, D.; Puchulu, M. E.; Hidalgo, M. d. V.; Blesa, M. A. Field Tests of the Solar Water Detoxification SOLWATER Reactor in Los Pereyra, Tucumán, Argentina. J. Sol. Energy Eng. 2007, 129, 127−134. (184) Horikoshi, S.; Nishimura, T.; Tsutsumi, H.; Serpone, N. Microwave Discharge Electrodeless Lamps. Part VIII: Continuous OnSite Solar Energy Remediation of Contaminated Water. Chem. Eng. Technol. 2016, 39, 102−107. (185) Sattler, C.; Müller, F.-J.; Riffelmann, K.-J.; Ortner, J.; Funken, K.-H. Concept and Economic Evaluation of an Industrial Synthesis of ε-Caprolactam via Solar Photooximation of Cyclohexane. J. Phys. IV 1999, 9 (Pr3), 723−727. (186) Funken, K.-H.; Müller, F.-J.; Ortner, J.; Riffelmann, K.-J.; Sattler, C. Solar Collectors versus Lamps − A Comparison of the Energy Demand of Industrial Photochemical Processes as Exemplified by the Production of ε-Caprolactam. Energy 1999, 24, 681−687. (187) Monnerie, N.; Ortner, J. Economic Evaluation of the Industrial Photosynthesis of Rose Oxide via Lamp or Solar Operated Photooxidation of Citronellol. J. Sol. Energy Eng. 2001, 123, 171−174. (188) Ravelli, D.; Protti, S.; Neri, P.; Fagnoni, M.; Albini, A. Photochemical Technologies Assessed: The Case of Rose Oxide. Green Chem. 2011, 13, 1876−1884. (189) Funken, K.-H.; Ortner, J.; Riffelmann, K.-J.; Sattler, C. New Developments in Solar Photochemistry. J. Inf. Rec. 1998, 24, 61−68. (190) Oelgemöller, M.; Bolte, M. Laboratory Profile of the ‘Applied and Green Photochemistry Research Group’ at James Cook University in Australia. Green Process. Synth. 2014, 3, 163−165.

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