Control of the Switching Speed of Photochromic Naphthopyrans

Nov 3, 2017 - An efficient synthesis of photochromic fused-naphthopyrans was developed. UV–vis or sunlight irradiation of these uncolored compounds ...
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Control of the Switching Speed of Photochromic Naphthopyrans through Restriction of Double Bond Isomerization Céu M. Sousa,† Jerome Berthet,‡ Stephanie Delbaere,‡ André Polónia,† and Paulo J. Coelho*,† †

Centro de Química - Vila Real, Universidade de Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal Université de Lille, CNRS UMR 8516, LASIR, BP83, F-59006 Lille, France

‡

S Supporting Information *

ABSTRACT: An efficient synthesis of photochromic fused-naphthopyrans was developed. UV−vis or sunlight irradiation of these uncolored compounds in solution led to the formation of a single colored photoisomer along with an unusual and uncolored bicyclic compound formed through an intramolecular photochemical Diels−Alder reaction. Both species faded thermally in the dark to the initial form. A mechanism for this transformation is proposed based on NMR studies of irradiated solutions. The new fused-naphthopyrans have been incorporated into hybrid organic− inorganic matrices affording light-yellow materials that develop intense red colorations under UV light and return to the initial uncolored state in just a few seconds, in the dark, at room temperature. These results are useful for the development of fast switching materials used in the production of photochromic lenses.

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INTRODUCTION Naphthopyrans are the most important photochromic molecules used by the ophthalmic lens industry to create photosensitive lenses that darken under sunlight and return to the uncolored state in the absence of direct sunlight.1 Behind this magical effect is a photochemical reaction, promoted by the UV light, that induces a pronounced structural transformation of the molecule via the cleavage of the pyran C−O bond and the formation of two isomeric opened species, absorbing intensively in the visible region due to their extended conjugation.2 When the light source is turned off, both opened colored species return thermally to the closed form (NP) restoring the uncolored state (Scheme 1). Through structural changes of the naphthopyran core, including the introduction of electron donating substituents and annelation of aromatic systems, it is possible to control the color exhibited after UV/ sunlight exposure and the fading speed in the dark.3 These photoactive molecules can be incorporated in organic−inorganic matrices leading to transparent uncolored materials.4 The chemical environment created by the matrix also has a huge effect on the system response allowing to tune the intensity and color developed under sunlight exposure. However, although the commercially available photochromic lenses acquire intense gray or brown colorations after 30 s of sunlight exposure, the complete bleaching in the dark takes near 8 min. In other words, following sunlight activation, once the wearer goes indoors, the lenses stay colored for too long.5 There are two reasons for this behavior: (i) under continuous irradiation conditions, the color intensity and the fading speed are inversely related; the present photochromic lenses are thus the result of a compromise between these two contradictory © 2017 American Chemical Society

needs (high color intensity and high speed); to ensure high color intensity, the industry uses compounds with slow fading kinetics. (ii) the pyran ring opening originates two photoproducts, designated as transoid-cis (TC) and transoid-trans (TT), that have similar absorption maxima but different thermal stabilities (Scheme 1). The TC is thermally more labile and fades quickly to the NP while the TT is more stable and fades slowly.6 As a result, the discoloration step follows a biexponential kinetics with two different rate constants, being the TT fading around 10 times slower than the TC fading which means that when the light source is removed there is initially a fast TC color decay followed by the slow TT decay. Consequently, although the coloration under UV light is quite fast, the fading in the dark is globally slow with a persistent residual color that can extend the complete discoloration to near 8 min. In the last years, we have explored an efficient structural change in naphthopyrans to prevent the formation of the more stable TT isomer, and thus to suppress the undesired residual color.7 Although the ophthalmic industry has explored almost all possible modifications of the naphthopyran molecule, there are very few examples of compounds substituted at the pyran double bond because, in fact, these substituents induce a decrease in the thermal stability of the photoisomers, due to steric constrains, increasing the fading kinetics which can even prevent photochromism at room temperature.8 Nonetheless, the presence of a bridge linking the 4 position (double bond) to the 5 position (naphthalene) does not preclude the opening Received: July 4, 2017 Published: November 3, 2017 12028

DOI: 10.1021/acs.joc.7b01669 J. Org. Chem. 2017, 82, 12028−12037

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The Journal of Organic Chemistry Scheme 1. Photochromic Equilibrium for the 2,2-Diphenyl-2H-naphtho[1,2-b]pyran

The synthesis of the fused-naphthopyran B was easier but the lifetime of the colored species was too low (63 ms) leading to a very light color intensity under sunlight.10 In this work, we report on a new synthetic strategy to achieve new polycyclic fused-naphthopyrans in only three steps starting from a substituted naphthol. These compounds were then introduced in hybrid organic/inorganic matrices providing uncolored materials that develop a red coloration under UV light and return in just a few seconds to the uncolored state, in the dark, at room temperature.

of the pyran cycle through UV irradiation, affording the TC isomer, but precludes its isomerization to the slow fading TT isomer (Scheme 2). Thus, such a system can only generate the Scheme 2. Photochromic Equilibrium for FusedNaphthopyrans A and B

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RESULTS AND DISCUSSION Synthesis. Naphthopyrans are usually prepared by reaction of naphthols with 1,1-diarylprop-2-yn-1-ols. This one-step reaction, catalyzed by acids, produces an ether intermediate which, through a series of consecutive intramolecular reactions (Claisen rearrangement, enolization, 1,5-hydrogen shift, and electrocyclization) leads to the in situ formation of the naphthopyrans and the loss of one water molecule.11 The reaction is quite general, easy to perform and the yields are acceptable. It has been shown that 1,1,3-triarylprop-2-yn-1-ols can also be used, thus leading to the formation of naphthopyrans substituted in the pyran double bond.12 The required diaryl- or triarylpropynols can be efficiently prepared by reaction of lithium acetylides with aromatic ketones while the synthesis of properly substituted naphthols is more laborious and requires different strategies. Recently, we reported that a bridge between the naphthalene core and the pyran double bond constrains the molecule, accelerating the thermal back reaction and thus leading to very fast switching systems and low colorations. To counterbalance this effect, we considered the use of ortho substituted phenyl or 1-naphthyl groups in the pyran sp3-carbon atom, which are known to increase the lifetime of photoisomers.13

fast fading photoisomer TC. We have proven that this idea works and allows a faster interchange between the uncolored and colored states of naphthopyrans A and B. The fusednaphthopyran A affords a single yellow photoisomer with a half-life time of 66 s that reverts completely to the uncolored state.9 However, while the synthesis of common naphthopyrans is quite expeditious, the synthesis of this particular fusednaphthopyran was not straightforward and required 7 steps. Scheme 3. Synthesis of Fused-Naphthopyrans 4a−e

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DOI: 10.1021/acs.joc.7b01669 J. Org. Chem. 2017, 82, 12028−12037

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single colored photoisomer. In fact, successive cycles of irradiation/dark showed that the system is quite reproducible, allowing to be switched between the uncolored and colored state in just a few seconds without any accumulation of residual color usually observed with common naphthopyrans due to the formation of the undesired colored TT (Figure 2, Movie S1,

Our new synthetic path to the fused-naphthopyrans started with the methyl 4-hydroxy-6-methoxy-2-naphthoate 1 prepared from p-methoxybenzaldehyde and possessing an ester function in the meta position, useful to construct the intramolecular bridge.14 We also prepared a series of five different substituted triarylpropynols 2a−e with an aromatic ring in the terminal position of the triple bond, through the reaction of aromatic ketones with phenylacetylene in the presence of n-BuLi. Condensation of methyl 4-hydroxy-6-methoxy-2-naphthoate 1 with triarylpropynols 2a−e, in the presence of a catalytic amount of acid (p-TSA), afforded naphthopyrans 3a−e in medium yield (36−73%) (Scheme 3). UV irradiation of these compounds at room temperature does not induce any color change, probably because the substituents in the 4 and 5 positions destabilize the opened photoisomer leading to a very fast fading and a very low concentration of the colored species which is undetectable to the naked eye. Addition of an excess of phenyllithium to naphthopyrans 3a−e, at 0 °C, followed by treatment with trifluoroacetic acid (TFA) gave the target fusednaphthopyrans 4a−e, with the bridge system, which were purified by chromatography and recrystallization to afford white solids in low yield (17−31%). The structures of compounds 3a−e and 4a−e were confirmed by 1H and 13C NMR spectroscopy, which indicated a singlet between 6.4 and 6.0 ppm, in the 1H spectra, assigned to the pyranic ethylenic proton (H-3), confirming the presence of a substituent in the 4 position, and a signal around 80 ppm in the 13C NMR spectra, characteristic of the sp3 pyran cycle carbon atom (C-2). The formation of the intramolecular bridge, in the fused-naphthopyrans 4a−e is corroborated by the disappearance of the carbonyl signal of the ester group around 170 ppm, the appearance of a signal around 50 ppm due to the new sp3 carbon atom linking the aromatic systems, and by the change in the pattern of the aromatic protons. Photochromic Properties of Naphthopyrans 4a−e in Solution. Colorless solutions of the fused-naphthopyrans 4a− e (10−3 M in CHCl3) were submitted to continuous UV−vis light irradiation (150 W ozone free Xe lamp), at 20 °C, to mimic sunlight conditions. A new absorption band centered at 485−500 nm emerged (Figure 1) and, when the light was turned off, it decreased quickly following a monoexponential decay (t1/2 = 6.6 s for 4b). This indicates the formation of a

Figure 2. UV−vis/dark cycles for the fused-naphthopyran 4b (CHCl3, 10−3 M) measured at 500 nm at 20 °C.

Solution 1 of the Supporting Information, SI). Under sunlight this solution developed also a reddish coloration that fades in few seconds in the dark (Movie S2, Sunlight sem som). The nature of the substituents at the C-sp3 atom has a significant effect on the stability of the colored forms.10 While the fused-naphthopyran 4a, substituted with two phenyl groups, did not show photochromic properties, under our experimental conditions, due probably to a very fast switching between the two states, the fused-naphthopyrans 4b−e, with more bulking substituents, led to colored species with various stabilities (Table 1). The naphthopyran 4b substituted by two Table 1. Maximal Wavelengths of the Colored Forms (λmax, nm), Absorption Variation (ΔAbs), Fading Rate Constants (kΔ, s−1), and Half-Life (s) for the Fused-Naphthopyrans 4a−e in CHCl3 Solutions (1.0 × 10−3 M at 20 °C) under UV−vis Continuous Irradiation fused-naphthopyrans Ar1 4a 4b 4c 4d 4e

Ph o-MeOPh Ph 1-Np 1-Np

Ar2

λmax (nm)

Δabs

kΔ (s−1)

t1/2 (s)

Ph o-MeOPh o-MePh Ph p-MeOPh

498 485 500 500

0.028 0.022 0.018 0.024

0.10 0.38 0.58 1.0

6.9 1.8 1.2 0.69

ortho-methoxy phenyl groups showed the highest lifetime (6.6 s) while naphthopyrans 4c−e originated colored photoisomers with a very short lifetime thus leading to a smaller color change. NMR Studies on UV Irradiated Solutions of Naphthopyrans 4a−e. The dynamics of these photosensitive compounds can be studied by NMR coupled to an irradiation system.15 This technique allows one to evaluate how many species are formed after UV irradiation, determine their structure, and follow their thermal evaluation, giving valuable information for the establishment of a reaction mechanism.

Figure 1. Absorption spectra of fused-naphthopyran 4b (CHCl3, 10−3 M) before (black) and after UV−vis irradiation (red) at 20 °C. 12030

DOI: 10.1021/acs.joc.7b01669 J. Org. Chem. 2017, 82, 12028−12037

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Figure 3. Aliphatic part of 1H NMR spectra of 4b in toluene-d8 at −60 °C, a) before hv, b) after 5 min of UV irradiation at 365 nm, and c) after 25 min of UV irradiation at 365 nm.

Figure 4. Time evolution of 4b in toluene-d8 a) under irradiation at 365 nm at −60 °C, b) during thermal relaxation at −60 °C, and c) during thermal relation at +60 °C.

between P2a and P2b (Keq = P2b/P2a = 9). Rising the temperature up to 22 °C did not modify the ratio, which can however be changed by heating the sample at 60 °C. In these conditions, both P2a and P2b are converted into the initial form 4b (Figure 4c), with the same value of rate constant (kΔ= 1.0 × 10−4 s−1). To characterize the structure of photoproducts, 2D NMR experiments were acquired after irradiation at −80 °C. In the 2D-HMBC (Figure 5), 1H−13C long-range correlations through three bonds are observed between aromatic proton H14 at 7.77 ppm and quaternary deshielded carbon C1 at 184 ppm, between protons H3 at 8.18 ppm and H6′a at 6.95 ppm and quaternary carbon C2 at 139.4 ppm, thus characterizing P1 as an opened TC merocyanine. This assignment is in

Due to the low lifetime of the photoproduct at room temperature, experiments were conducted at low temperature to stabilize them. Upon UV irradiation (λirr = 365 nm, −60 °C) a solution of naphthopyran 4b, in toluene-d8, turned red. 1H NMR spectra highlighted the presence of new signals representing three photoproducts P1, P2a, and P2b (Figure 3) whose dynamics could be studied by monitoring the signals of the methoxy groups between 3.0 and 3.5 ppm. Under UV light P1 is the first photoproduct to be formed and is then converted into a mixture of P2a and P2b (Figure 4a) The monitoring of the thermal evolution at −60 °C (Figure 4b) indicated that P1 returns back to the initial form 4b (kΔ = 3.3 × 10−5 s−1), while a thermal equilibrium is established 12031

DOI: 10.1021/acs.joc.7b01669 J. Org. Chem. 2017, 82, 12028−12037

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Figure 5. Overlapping of 1H−13C HMBC (black correlations) and 1H−13C HSQC (gray correlations) experiments of 4b in toluene-d8 at −80 °C after UV irradiation at 365 nm to characterize P1 and P2a.

and P1, both P2a and P2b do not absorb at wavelengths higher than 350 nm (Figure 6). Knowing the nature of photoproducts obtained after irradiation with 365 nm, we decided to irradiate a fresh sample of 4b, in the same conditions, but with 313 nm. The same photoproducts were formed but their ratio varied greatly. Indeed, UV irradiation at 313 nm leads almost quantitatively to the merocyanine TC = P1 (Figure 7a). Amazingly, by applying such light to a sample previously submitted to 365 nm-light, the two cyclopropane photoproducts (P2a and P2b) bleached totally toward the merocyanine TC = P1 (Figure 7b). According to the structures of the photoproducts and the profiles of concentrations measured upon irradiation with 313 or 365 nm light, a plausible mechanism can be proposed. The fused-naphthopyran 4b absorbs UV light leading, by ring opening of the pyran, to merocyanine P1 with a maximal wavelength of absorption at 500 nm. Upon continuous 365 nm irradiation, P1 reaches a maximal concentration and is then photochemically converted to P2a and P2b which accumulate. The formation of a colorless cyclopropane derivative by irradiation of an opened naphthopyran merocyanine has already been reported by Irie et al.16 and is associated with a concerted intramolecular photochemical (4 + 2) Diels−Alder type reaction (Scheme 4).17 P2a and P2b absorb only below 350 nm. Therefore, these compounds are not photoreactive at 365 nm but are photoconverted with 313 nm light into the opened form P1. In addition, at +60 °C, P2a/P2b are thermally converted into the initial closed naphthopyran, probably by an ionic mechanism involving the heterolytic breaking of the C−O bond followed by cyclopropane opening and formation of compound P1 that returns thermally to the initial naphthopyran (Scheme 5).18 Thus, the colorless fused-naphthopyran 4b exhibits a completely reversible behavior: Under UV irradiation (λirr = 365 nm) it is converted into the expected unstable colored photoisomer TC that photoisomerizes into the uncolored bicyclic P2a/2b. The latter are thermally unstable and, in the absence of light, return slowly to 4a through TC or when

agreement with the UV−visible profile recorded after irradiation with the characteristic band at 500 nm for an open naphthopyran (Figure 6).

Figure 6. UV−visible spectra of a) initial form 4b (black), mixture of 4b and P1 (red), and mixture of P2a and P2b (blue) in toluene-d8 at −60 °C.

Concerning the photoproduct P2a, it is assigned to the structure drawn in Figure 5. The cyclopropane is well identified by three aliphatic carbons presenting long-range correlations with protons: C2 at 38.5 ppm with H6′ at 5.56 ppm and H6′a at 7.05 ppm; C4 at 45.5 ppm with H5 at 6.61 ppm; or direct correlation between C3 at 79.7 ppm with H3 at 7.30 ppm (evidenced in HSQC). Finally, P2b was identified as a conformational isomer of P2a as a consequence of the geometrical orientation of methoxyphenyl groups (see SI data). The measurement of the UV−vis spectra of the 4b solution before irradiation, after UV irradiation (λirr = 365 nm) and thermal relaxation at −60 °C showed that in contrast with 4b 12032

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Figure 7. Time evolution of 4b in toluene-d8 at −60 °C a) upon irradiation with 313 nm light and b) upon first irradiation with 365 nm, then with 313 nm.

Scheme 4. Mechanism for the UV Promoted Transformation between P1 into P2

Scheme 6. General Mechanism for the Photochromic Behavior of Fused-Naphthopyrans 4a−e

Scheme 5. Mechanism for the Thermal Transformation of P2 into P1

their properties can be adjusted through the introduction of substituents in some particular positions but also because they can be incorporated in polymeric materials without loss of their activity, although the media affects their performance.4 In particular, the activation (ring-opening) and fading (ringclosure) kinetic rates are deeply dependent on the rigidity of the materials, the core structure and the free volume available to the dye since these molecules undergo substantial changes in molecular shape when switching between colorless and colored states. Organic−inorganic hybrid matrices are the most used materials to produce photochromic ophthalmic lenses. Usually the naphthopyran is dispersed within the matrix precursors which are then applied to the surface of the lens and subject to

exposed to 313 nm light, they are quickly converted back to 4a also through TC (Scheme 6) The fused-naphthopyrans 4a,c−e exhibited a similar photochromic behavior but while compound 4a, presenting two phenyl groups at the sp3 carbon atom, afforded the respective photoisomer P1 and the bicyclic compound P2, compounds 4c−e, which have two different aromatic systems at the sp3 carbon atom afforded two photoisomers of P1 and other two diastereoisomeric forms of the bicyclic compound P2 (for more details see the SI) Photochromic Organic−Inorganic Hybrid Materials. Naphthopyrans are very versatile compounds not only because 12033

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The Journal of Organic Chemistry a thermal process that promotes the solvent evaporation and the matrix network formation.19 To test the usefulness of the new fused-naphthopyrans, we prepared some simple organic−inorganic hybrid materials, based on mixtures of GPTMS ((3-glycidoxypropyl)methyldiethoxysilane) and Jeffamines) (polyoxyalkylenediamines of different molecular weights) by the sol−gel method and doped them with compounds 4a−e.20 To optimize the matrix composition, the compound 4b was dispersed in mixtures of GPTMS and Jeffamines and cured at 50 °C for 3 days producing almost transparent yellowish materials with 2 mm thickness. UV irradiation of these materials at room temperature using a high-power laser (405 nm, 200 mW) at 20 °C led to the development of a red coloration (Figure 8) which

Table 3. Maximal Wavelengths of the Colored Forms (λmax, nm), Fading Rate Constants (k, s−1) and Half-Life (s) for the Fused-Naphthopyran 4b, 4c, and 4e in GPTMS/Jeffamine 600 at 20 °C under Continuous Irradiation Using a HighPower Laser (405 nm, 200 mW) fused-naphthopyrans 4b 4c 4e

o-MeOPh Ph 1-Np

o-MeOPh o-MePh p-MeOPh

λmax (nm)

Δabs

kΔ (s−1)

t1/2 (s)

500 485 500

0.36 0.14 0.24

0.50 1.5 2.2

1.4 0.46 0.32

coloration under UV light (6 s) and very fast decoloration (less than 10 s) with a noticeable color change (Δabs = 0.36). Furthermore, after activation and development of the red coloration, the system reverts completely to the initial state rapidly (t1/2 = 0.3−1.4 s) without any accumulation of residual color due to the presence of a single fast fading colored species allowing to perform successive and reproducible irradiation cycles (Figure 9). However, if extended irradiation times are

Figure 8. Photos of the GPTMS/Jeffamine sol−gel material doped with fused-naphthopyran 4b before and after UV irradiation with a high-power laser (405 nm, 200 mW) at 20 °C.

disappeared completely in just a few seconds after removal of the light source (Movie S3, Sol Gel 1). The nature of the Jeffamine cross-linker influences mainly the intensity of the coloration obtained after irradiation (Table 2). At 20 °C these Table 2. Maximal Wavelengths of the Colored Forms (λmax, nm), Fading Rate Constants (k, s−1), and Half-Life (s) for the Fused-Naphthopyran 4b in Different Matrices at 20 °C under Continuous Irradiation Using a High-Power Laser (405 nm, 200 mW) matrix

λmax (nm)

Δabs

kΔ (s−1)

t1/2 (s)

GPTMS/Jeffamine 400 GPTMS/Jeffamine 600 GPTMS/Jeffamine 900

500 500 500

0.10 0.36 0.06

0.43 0.50 0.54

1.6 1.4 1.3

Figure 9. Successive laser (405 nm, 200mw) (6s)/dark (1 min) cycles for fused-naphthopyran 4b in a GPTMS/Jeffamine 600 matrix at 20 °C.

used, then the maximal absorbance decreases progressively due, probably, to the formation of the colorless bicyclic species P2 which fades more slowly.

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CONCLUSIONS The introduction of a bridge between the pyran double bond and the naphthalene core is an efficient strategy to increase the switching speed of photochromic naphthopyrans. Such fusednaphthopyrans can be efficiently prepared in just 3 steps from a substituted naphthol, and show photochromic properties at room temperature, in solution or dispersed in organic− inorganic matrix when exposed to the UV or sunlight (heliochromism). NMR analysis of irradiated solutions of these compounds shows that the UV light promotes the opening of the pyran ring affording only one colored photoisomer with a TC configuration that undergoes an unusual photochemical intramolecular Diels−Alder reaction toward an uncolored bicyclopropane derivative. The latter is thermally and photochemically unstable and reverts back to initial naphthopyran through the TC photoisomer. Therefore, these fused-naphthopyrans undergo a reversible photochemical transformation allowing them to switch between the uncolored and colored states in less than 10 s without any accumulation of residual color commonly observed with naphthopyrans. These

materials clearly develop a red coloration with a maximum wavelength of absorption at 500 nm which fades in a few seconds (t1/2 = 1.3−1.6 s) following a monoexponential decay confirming the formation of a single colored species. The highest variation of the optical density was observed with the Jeffamine 600 and thus this composition was used to evaluate the performance of the fused-naphthopyrans 4a−e (Table 3). Compound 4d showed a limited solubility under these conditions and was not used. The material doped with compound 4a, with two phenyl groups attached to the pyran sp3 carbon, did not show, as expected, any color variation under UV light indicative of the formation of rather unstable colored forms. The introduction of two methoxy groups (4b), one methyl in the ortho position of the phenyl rings (4c), or one naphth-1-yl group (4e) increases the lifetime of the colored species, hindering the ring closure of the colored species. The materials doped with these three compounds show a fast 12034

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The Journal of Organic Chemistry

1H). 13C NMR (100 MHz, CDCl3): 144.6, 138.8, 134.6, 131.7, 130.1, 129.4, 128.7, 128.6, 128.3, 128.1, 127.9, 126.8, 126.5, 125.4, 125.3, 124.7, 124.6, 122.4, 91.7, 88.2, 74.8. EI-MS (TOF) m/z (%): 334 (M+, 11), 333 (14), 318 (22), 315 (16), 289 (9), 257 (17), 241 (44), 239 (51), 232 (100), 229 (72), 226 (35), 215 (17), 155 (58), 127 (71), 105 (40), 77 (5). HRMS (EI-TOF) m/z: [M]+ Calcd. for C25H18O 334.1358; Found 334.1364. 1-(4-Methoxyphenyl)-1-(naphthalene-1-yl)-3-phenylprop-2-yn-1ol 2e. 2e was obtained from 4-methoxyphenyl 1-naphthyl ketone (1.5 g, 5.72 mmol) and isolated as an yellow oil by column chromatography (0−10% ethyl acetate/petroleum ether) (0.869 g, 42%). IR (cm−1): 3435, 3052, 2947, 2314, 1245. 1H NMR (400 MHz, CDCl3): 8.36 (d, J = 8.4 Hz, 1H), 8.26 (dd, J = 1.2 Hz, J = 7.5 Hz, 1H), 8.00 (t, J = 7.8 Hz, 2H), 7.70−7.30 (m, 10H), 6.98 (d, J = 8.5 Hz, 2H), 3.92, (s, 3H, OCH3), 3.25 (s, 1H).13C NMR (100 MHz, CDCl3): 159.2, 139.1, 137.1, 134.6, 131.7, 130.2, 129.4, 128.62, 128.55, 128.3, 127.9, 127.0, 125.4, 125.3, 124.8, 124.4, 122.6, 113.8, 92.1, 87.8, 74.3, 55.2. EI-MS (TOF) m/z (%): 364 (M+, 20), 348 (51), 347 (47), 302 (30), 262 (62), 259 (57), 256 (64), 239 (35), 231 (40), 226 (41), 215 (40), 155 (27), 135 (100), 127 (57), 102 (24). HRMS (EI-TOF) m/z: [M]+ Calcd. for C26H20O2 364.1463; Found 364.1466. Synthesis of Naphthopyrans 3a−e. Methyl 9-methoxy-2,2,4triphenylnaphtho[1,2-b]pyran-5-carboxylate 3a. A solution of methyl-4-hydroxy-6-methoxy-2-naphthoate 1 (420 mg, 1.80 mmol), 1,1,3-triphenylprop-2-yn-1-ol 2a (490 mg, 1.80 mmol) and ptoluenesulfonic acid hydrate (catalytic) in CHCl3 (20 mL) was stirred at room temperature. After 5 h another equiv of 1,1,3-triphenylprop-2yn-1-ol was added and the solution maintained under stirring during 18 h. The solvent was removed under reduced pressure and the product 3a was isolated by column chromatography (silica gel, 0−10% ethyl acetate/petroleum ether) and purified by recrystallization from CH2Cl2/petroleum ether (396 mg, 44%). Mp: 110.8−114.0 °C. IR (cm−1): 2952, 2319, 1705, 1205. 1H NMR (400 MHz, CDCl3): 7.9− 7.7 (m, 7H), 7.6−7.2 (m, 12H), 6.32 (s, 1H), 4.14 (s, 3H), 3.28 (s, 3H). 13C NMR (100 MHz, CDCl3): 168.7, 159.3, 149.2, 144.2, 140.5, 137.7, 130.3, 128.5, 128.3, 128.1, 127.9, 127.7, 127.5, 127.4, 127.1, 126.8, 125.6, 123.8, 119.8, 116.6, 101.1, 83.0, 55.6, 51.4. EI-MS (TOF) m/z (%):498 (M+, 40), 466 (100), 438 (26), 421 (90), 389 (42), 378 (20), 361 (41), 318 (24), 289 (41), 165 (40). HRMS (EI-TOF) m/z: [M]+ Calcd. for C34H26O4 498.1831; Found 498.1850. Methyl 9-Methoxy-2,2-bis(2-methoxyphenyl)-4-phenylnaphtho[1,2-b]pyran-5-carboxylate 3b. A solution of methyl-4-hydroxy-6methoxy-2-naphthoate 1 (400 mg, 1.72 mmol), 1,1-bis(2-methoxyphenyl)-3-phenylprop-2-yn-1-ol 2b (593 mg, 1.72 mmol) and p-TSA (catalytic) in CHCl3 (25 mL) was heated under reflux. After 1.5 h another 0.5 equiv of 2b was added and the mixture maintained under reflux for an additional 3 h. Water was added (40 mL) and the aqueous phase was extracted with ethyl acetate (3 × 30 mL). The organic phases were dried (Na2SO4), and the solvent was removed under reduced pressure. The residue was crystallized from CH2Cl2/ petroleum ether to give 3b as white crystals (705 mg, 73%). Mp: 223.6−227.0 °C. IR (cm−1): 2941, 1710, 1210. 1H NMR (400 MHz, CDCl3): 7.88 (dd, J= 7.77 Hz, J = 1.52 Hz, 2H), 7.82 (d, J = 2.5 Hz, 1H), 7.61 (s, 1H), 7.58 (d, J = 8.92 Hz, 1H), 7.34−7.20 (m, 4H), 7.20−7.15 (m, 2H), 7.15−7.00 (m, 3H), 6.85 (t, J = 7.5 Hz, 2H), 6.69 (d, J = 8.16 Hz, 2H), 6.25 (s, 1H), 3.93 (s, 3H), 3.47 (s, 6H), 3.06 (s, 3H). 13C NMR (100 MHz, CDCl3): 169.0, 159.0, 157.0, 149.5, 141.2, 136.0, 131.1, 130.0, 129.2, 128.5, 128.4, 128.2, 127.5, 127.0, 126.7, 125.5, 123.3, 119.8, 119.5, 116.9, 112.4, 101.8, 80.6, 55.5, 55.3, 51.4. EI-MS (TOF) m/z (%): 558 (M+, 99), 526 (67), 512 (18), 480 (24), 451 (30), 435 (20), 419 (100), 395 (32), 391 (25), 368 (99), 353 (51), 346 (54), 332 (23), 315 (29), 251 (18), 214 (14), 147 (9). HRMS (EI-TOF) m/z: [M]+ Calcd. for C36H30O6 558.2042; Found 558.2051. Methyl 9-Methoxy-2-(2-methylphenyl)-2,4-diphenylnaphtho[1,2b]pyran-5-carboxylate 3c. A solution of methyl-4-hydroxy-6methoxy-2-naphthoate 1 (650 mg, 2.80 mmol) 1-(2-methylphenyl)3-phenylprop-2-yn-1-ol 2c (835 mg, 2.80 mmol) and p-TSA (catalytic) in CHCl3 (25 mL) was stirred at room temperature. After 5 h, another 0.5 equiv of 2c was added, and the solution was kept

results are useful for the development of fast switching materials used in the production of photochromic lenses.

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EXPERIMENTAL SECTION

General Methods. The reactions were monitored by thin-layer chromatography (TLC) on aluminum plates precoated with silica gel 60 F254 (0.25 mm). Column chromatography was performed on silica gel 60 (70−230 mesh). The new compounds were determined to be >95% pure by 1H NMR spectroscopy. NMR spectra in CDCl3 were recorded at 298 K using a 400 or 300 MHz spectrometer. Chemical shifts (δ) are reported in parts per million. FTIR spectrometer, with diamond crystal cell ATR was used to acquire the absorption spectra of the compounds (wavenumbers in cm−1). Methyl 6-methoxy-3carboxylate-naphth-1-ol 1,14 2,2′-dimethoxybenzophenone,21 1-naphthy phenyl ketone,22 and 4-methoxyphenyl 1-naphthyl ketone23 were prepared using published methods. Synthesis of Triarylprop-2-yn-1-ols 2a−e. n-Butyllithium (1.6 M in hexanes, 2 equiv) was slowly added (5 min) to a cold (0 °C) solution of phenylacetylene (1.1 equiv) in dry THF (25 mL) and stirred for 1 h. The diarylketone (1 equiv) was then added in a single portion to the solution and the mixture was stirred at room temperature for 24 h. The solvent was evaporated under reduced pressure, water (50 mL) was added, and the aqueous phase was extracted with ethyl acetate (3 × 50 mL). The combined organic phases were dried with anhydrous Na2SO4, concentrated under reduced pressure, and the residual product was purified by column chromatography or recrystallization. 1,1,3-Triphenylprop-2-yn-1-ol 2a. 2a was obtained from benzophenone (2.00 g, 10.9 mmol) and isolated as a yellow oil by column chromatography (silica gel, 0−10% ethyl acetate/petroleum ether) (1.020 g; 31%). IR (cm−1): 3549, 3061, 2221, 1160. 1H NMR (400 MHz, CDCl3): 7.87−7.85 (m, 2H), 7.70 (dd, J = 2 Hz, J = 6 Hz, 2H), 7.60−7.4 (m, 9H), 3.14 (s, 1H, OH). 13C NMR (100 MHz, CDCl3): 145.0, 131.7, 128.6, 128.3, 127.7, 126.5, 126.0, 122.4, 91.7, 87.2, 74.80. EI-MS (TOF) m/z (%): 284 (M+, 20), 267 (13), 206 (53), 183 (28), 178 (75), 165 (17), 129 (38), 105 (100), 77 (80). HRMS (EI-TOF) m/z: [M]+ Calcd. for C21H16O 284.1201; Found 284.1210. 1,1-Bis(2-methoxyphenyl)-3-phenylprop-2-yn-1-ol 2b. 2b was obtained from 2,2′-dimethoxybenzophenone (5.65 g, 23.3 mmol) and isolated as an off-white powder (7.56 g, 94%) after recrystallization from ethyl acetate/hexane. Mp 127.1−130.1 °C. IR (cm−1): 3482, 2932, 1229, 1248. 1H NMR (400 MHz, CDCl3): 7.79 (dd, J = 7.8 Hz, J = 1.7 Hz, 2H), 7.46 (m, 2H), 7.28 (m, 5H), 6.97 (td, J = 1.0 Hz, J = 7.6 Hz, 2H), 6.89 (d, J = 8.2 Hz, 2H), 3.70 (s, 6H, OMe). 13C NMR (75 MHz, CDCl3): 156.8, 132.0, 131.8, 129.0, 128.1 (two carbons), 128.0, 123.4, 120.5, 112.5, 90.9, 85.2, 73.5, 55.9. EI-MS (TOF): m/z (%): 344 (19), 329 (29), 313 (100), 297 (47), 285 (10), 269 (18), 265 (16), 252 (20), 239 (22), 236 (31) 225 (20), 211 (17), 200 (14), 176 (43), 135 (56). HRMS (EI-TOF) m/z: [M]+ Calcd. for C23H20O3: 344.1412; found: 344.1411. 1-(2-Methylphenyl)-1,3-diphenylprop-2-yn-1-ol 2c. 2c was obtained from 2-methylbenzophenone (1.00 g, 5.10 mmol) and isolated as a yellow oil without purification (1.52 g; 100%): IR (cm−1): 3436, 3059, 2957, 2214, 1247. 1H NMR (400 MHz, CDCl3): 8.04 (dd, J = 7.5 Hz, J = 1.5 Hz), 7.62 (dd, J = 8.1 Hz, J = 1.5 Hz, 2H), 7.53 (dd, J = 5.5 Hz, J = 2 Hz, 2H), 7.45−7.30 (m, 8H), 7.34 (m, 1H), 2.23 (s, 3H). 13 C NMR (100 MHz, CDCl3): 144.0, 141.6, 136.4, 132.1, 131.7, 128.4, 128.3 (two carbons), 128.0, 127.9, 126.6, 126.0, 125.5, 122.5, 90.9, 87.4, 74.4, 21.0. EI-MS (TOF) m/z (%): 298 (39), 283 (100), 265 (20), 220 (24), 207 (33), 206 (52), 205 (22), 202 (22), 196 (25), 195 (64), 192 (24), 191 (27), 178 (62), 129 (33). HRMS (EI-TOF) m/z: [M]+ Calcd. for C22H18O 298.1358; Found 298.1359. 1-(Naphth-1-yl)-1,3-diphenylprop-2-yn-1-ol 2d. 2d was obtained from 1-naphthyl phenyl ketone (1.00 g, 4.31 mmol) and isolated by column chromatography (silica gel, 0−10% ethyl acetate/petroleum ether) as an orange oil (1.22 g, 85%). Mp 131.6−133.4 °C. IR (cm−1): 3050, 2918, 2314, 1158. 1H NMR (400 MHz, CDCl3): 8.40 (d, J = 8.5 Hz, 1H), 8.32 (dd, J = 1.1 Hz, J = 7.4 Hz, 1H), 8.03 (t, J = 8.3 Hz, 2H), 7.83 (dd, J = 2 Hz, J = 5.5 Hz, 2H), 7.70−7.30 (m, 11), 3.25 (s, 12035

DOI: 10.1021/acs.joc.7b01669 J. Org. Chem. 2017, 82, 12028−12037

Article

The Journal of Organic Chemistry under stirring at room temperature for 19 h. Then another 0.5 equiv of 2c were then added. After 24 h the solvent was removed, and the product was isolated by column chromatography (silica, 0−5% ethyl acetate/petroleum ether) and purified by recrystallization using CH2Cl2/ petroleum ether and obtained as white crystals (520 mg, 36%). Mp 200.0−201.4 °C. IR (cm−1): 2952, 1704, 1201. 1H NMR (400 MHz, CDCl3): 7.96 (m, 1H), 7.9−7.8 (m, 3H), 7.8−7.6 (m, 2H), 7.6−7.2 (m, 12H), 6.13 (s, 1H), 4.09 (s, 3H), 3.29 (s, 3H), 2.42 (s, 3H). 13C NMR (100 MHz, CDCl3): 168.7, 159.2, 149.4, 144.4, 140.5, 140.1, 137.5, 137.2, 132.5, 130.3, 128.8, 128.5, 128.4, 128.2, 127.9, 127.4 (two), 126.9, 126.7, 125.5, 125.1, 123.6, 119.8, 116.4, 101.2, 83.9, 55.5, 51.4, 21.5. EI-MS (TOF) m/z (%): 512 (M+, 100), 480 (41), 435 (24), 421 (26), 389 (28), 361 (21), 289 (23), 180 (36). HRMS (EI-TOF) m/z: [M]+ Calcd. for C35H28O4 512.1988; Found 512.1992. Methyl 9-Methoxy-2-(naphth-1-yl)-2,4-diphenylnaphtho[1,2-b]pyran-5-carboxylate 3d. A solution of methyl-4-hydroxy-6-methoxy2-naphthoate 1 (400 mg, 1.72 mmol), 1-(naphth-1-yl)-1,3-diphenylprop-2-yn-1-ol 2d (575 mg, 1.72 mmol) and p-TSA (catalytic) in CHCl3 (20 mL) was stirred at room temperature. After 2 h another 1.0 equiv of 2d was added, and the solution was stirred at room temperature for 18 h. Water (40 mL) was added, and the aqueous phases was extracted with ethyl acetate (2 × 25 mL). The combined organic layers were dried (Na2SO4), and the solvent was removed under vacuum to afford the crude product, which was purified by chromatography column (silica, 0−10% CH2Cl2/petroleum ether) and recrystallized from CH2Cl2/petroleum ether to give 3d as white crystals (452 mg; 48%). Mp: 274.6−276.8 °C. IR (cm−1): 3030, 2946, 1716, 1192. 1H NMR (400 MHz, CDCl3): 8.42 (d, J = 8.5 Hz, 1H), 8.12 (d, J = 7.1 Hz, 1H), 7.74 (d, J = 8.0 Hz, 2H), 7.66 (s, 1H), 7.64− 7.50 (m, 4H), 7.50−7.20 (m, 11H), 7.03 (d, J = 8.5 Hz, 1H), 6.05 (s, 1H), 3.90 (s, 3H, OCH3), 3.15 (s, 3H, OCH3). 13C NMR (100 MHz, CDCl3): 168.7, 159.0, 149.5, 145.3, 140.5, 137.1, 136.8, 135.0, 130.8, 130.0, 129.8, 128.9, 128.5, 128.4, 128.3, 127.9, 127.5 (four carbons), 127.3, 126.8, 126.7, 125.5, 125.2, 125.1, 124.4, 123.6, 119.9, 116.5, 101.4, 84.3, 55.4, 51.5. EI-MS (TOF): m/z (%): 548 (100), 516 (87), 471 (17), 439 (20), 411 (20), 228 (15), 215 (18), 344 (19), 329 (29), 313 (100), 297 (47), 285 (10), 269 (18), 265 (16), 252 (20), 239 (22), 236 (31) 225 (20), 211 (17), 200 (14), 176 (43), 135 (56). HRMS (EI-TOF) m/z: [M]+ Calcd. for C38H28O4 548.1988; Found 548.1985. Methyl 9-Methoxy-2-(naphth-1-yl)-2-(4-methoxyphenyl)-4phenylnaphtho[1,2-b]pyran-5-carboxylate 3e. A solution of methyl-4-hydroxy-6-methoxy-2-naphthoate 1 (300 mg, 1.29 mmol), 1-(4methoxyphenyl)-1-(naphthalene-1-yl)-3-phenylprop-2-yn-1-ol 2e (470 mg, 1.29 mmol) and p-TSA (catalytic) in CHCl3 (20 mL) was stirred at room temperature. After 4 h another 1.0 equiv of 2e was added, and the solution was kept at room temperature for 17 h. Water (40 mL) was added and the aqueous phase was extracted with ethyl acetate (3 × 25 mL). The organic phase was dried with Na2SO4 and concentrated under reduced pressure. The product was isolated by column chromatography (silica, 0−10% CH2Cl2/petroleum ether) and purified by recrystallization from CH2Cl2/petroleum ether to afford 3e as white crystals (283 mg, 38%). Mp: 249.0−252.9 °C. IR (cm−1): 3021, 2952, 1721, 1204. 1H NMR (400 MHz, CDCl3): 8.34 (d, J = 8.4 Hz, 1H), 8.05 (d, J = 7.2 Hz, 1H), 7.69 (d, J = 8.0 Hz, 2H), 7.61 (s, 1H), 7.55 (m, 2H), 7.5−7.2 (m, 10H), 6.98 (dd, J = 1.5 Hz, J = 8.7 Hz, 1H), 6.74 (d, J = 8.4 Hz), 6.04 (s, 1H), 3.84 (s, 3H), 3.68 (s, 3H), 3.11 (s, 3H). 13C NMR (100 MHz, CDCl3): 168.8, 159.0, 158.8, 149.4, 140.6, 137.3, 137.1 (2 signals), 135.0, 130.8, 130.1, 129.7, 128.9, 128.5, 128.3, 128.2, 128.0, 127.6, 127.4, 127.0, 126.8, 125.5, 125.2, 125.1, 124.5, 123.6, 119.9, 116.6, 113.7, 101.4, 83.9, 55.4, 55.2, 51.5. EI-MS (TOF) m/z (%): 578 (M+, 100), 546 (94), 518 (23), 501 (23), 487 17), 451 (31), 438 (32), 411 (23), 305 (22), 258 (51), 215 (27). HRMS (EI-TOF) m/z: [M]+ Calcd. for C39H30O5: 578.2093; found 578.2109. Synthesis of Fused-Naphthopyrans 4a−e. Four equiv of PhLi (1.8 M in dibutyl ether) were added to a solution of naphthopyrans 3a−e (0.4 mmol) in dry THF (5 mL) at 0 °C under constant stirring. After 1 h the solvent was evaporated under reduced pressure, and

water was added. The aqueous phase was extracted with ethyl acetate and the organic phases were washed with water, dried (Na2SO4) and concentrated under reduced pressure affording an oil. TFA (1 mL) was added to the oil at room temperature, and the mixture acquired an intense blue coloration. The reaction was completed overnight (confirmed by TLC) and water was added. A saturated solution of NaHCO3 was added until the gas evolution was complete and the aqueous phase was extracted with ethyl acetate (3 × 30 mL). The organic layers were combined, washed with water (6 × 40 mL) and dried with Na2SO4. The product was isolated by chromatography column (silica, 0−5% ethyl acetate/petroleum ether) and purified by recrystallization (CH2Cl2/petroleum ether). 12-Methoxy-2,2,8,8-tetraphenyl-2H,8H-naphtho[1,2,3-de]naphtho[1,2-b]pyran 4a. (46 mg, 19% yield). IR (cm−1): 3024, 2952, 1598, 1233. 1H NMR (300 MHz, CDCl3): 7.81 (d, J = 7.2 Hz, 1H), 7.6 (d, J = 2.5 Hz, 1H), 7.48 (d, J = 8.3 Hz, 1H), 7.14−7.42 (m, 18H), 7.07 (m, 2H), 6.83 (d, J = 7.1 Hz, 4H), 6.76 (s, 1H), 6.42 (s, 1H), 3.97 (s, 3H). 13C NMR (75 MHz, CDCl3): 157.6, 146.3, 142.2, 144.4, 143.6, 136.8, 131.6, 130.6, 130.4, 129.7, 129.6, 129.4, 128.0, 127.7, 127.6, 127.3, 127.2, 126.7, 126.2, 124.7, 123.7, 120.8, 120.4, 118.9, 116.2, 100.4, 83.6, 59.5, 55.5. EI-MS (TOF) m/z (%): 604 (M+, 11), 527 (75), 450 (17), 435 (14), 407 (12), 247 (100). HRMS (EI-TOF) m/z: [M]+ Calcd. for C45H32O2 604.2358; Found 604.2379. 12-Methoxy-2,2-bis(2-methoxyphenyl)-8,8-diphenyl-2H,8Hnaphtho[1,2,3-de]naphtho[1,2-b]pyran 4b. (80 mg, 30% yield). IR (cm−1): 3021, 2935, 1598, 1239. 1H NMR (300 MHz, CDCl3): 7.83 (dd, J = 7.2 Hz, 1H), 7.72 (d, J = 2.5 Hz, 1H), 7.49 (dd, J = 7.7 Hz, J = 1.4 Hz, 2H), 7.46 (d, J = 9.0 Hz, 1H), 7.12−7.34 (m, 10H), 7.06 (d, J = 7.4 Hz, 1H), 7.03 (dd, J = 9.0 Hz, J = 2.5 Hz, 1H), 6.86 (d, J = 7.8 Hz, 4H), 6.7−6.8(m, 5H), 6.63 (s, 1H), 3.97 (s, 3H), 3.44 (s, 6H). 13C NMR (75 MHz, CDCl3): 157.3, 156.8, 146.6, 146.5, 143.4, 136.7, 132.2, 131.6, 130.5, 130.3, 129.5, 129.3, 129.2, 128.4, 128.1, 127.5, 127.1, 126.5, 126.0, 125.1, 123.6, 120.4, 120.1, 119.9, 118.6, 116.2, 112.3, 100.8, 81.2, 59.4, 55.5, 55.2. EI-MS (ESI) m/z (%): 664 (M+, 30), 587 (63), 557 (100), 480 (24), 465 (17). HRMS (ESI-TOF) m/ z: [M + H]+ Calcd. for C47H37O4 665.26902; Found 665.26864. 12-Methoxy-2-(2-methylphenyl)-2,8,8-triphenyl-2H,8H-naphtho[1,2,3-de]naphtho[1,2-b]pyran 4c. (77 mg, 31% yield). IR (cm−1): 3059, 2947, 1598, 1233. 1H NMR (300 MHz, CDCl3): 7.78 (d, J = 7.4 Hz, 1H), 7.59 (d, J = 2.6 Hz, 1H), 7.47 (d, J = 8.8 Hz, 1H), 7.02−7.38 (m, 20H), 6.92 (d, J = 7.7 Hz, 2H), 6.95 (td, J = 7.7 Hz, J = 1.5 Hz, 1H), 6.80 (d, J = 7.9 Hz, 2H), 6.77 (s, 1H), 6.26 (s, 1H), 3.93 (s, 3H), 2.22 (s, 3H). 13C NMR (75 MHz, CDCl3): 157.5, 146.5, 146.4, 144.6, 143.6, 140.5, 137.3, 136.9, 132.3, 131.7, 130.9, 130.5, 130.3, 129.7, 129.4, 129.2, 128.8, 128.2, 127.8, 127.7, 127.6, 127.6, 127.0, 126.8, 126.7, 126.3, 126.1, 125.1, 124.8, 123.7, 120.7, 120.1, 118.9, 116.0, 100.5, 84.4, 59.5, 55.4, 21.3. EI-MS (TOF) m/z (%): 618 (M+, 17), 541 (100), 527 (12), 450 (13). HRMS (EI-TOF) m/z: [M]+ Calcd. for C46H34O2 618.2559; Found 618.2557. 12-Methoxy-2-(naphth-1-yl)-2,8,8-triphenyl-2H,8H-naphtho[1,2,3-de]naphtho[1,2-b]pyran 4d. (45 mg, 17% yield). IR (cm−1): 3059, 2947, 1593, 1221. 1H NMR (300 MHz, CDCl3): 8.36 (d, J = 8.6 Hz, 1H), 7.74−7.81 (m, 2H), 7.70 (d, J = 8.4 Hz, 1H), 7.47 (d, J = 2.5 Hz, 1H), 7.36−7.46 (m, 4H), 7.19−7.36 (m, 11H), 7.14 (t, J = 7.9 Hz, 2H), 6.98 (m, 4H), 6.95 (dd, J = 9.1 Hz, J = 2.5 Hz, 1H), 6.75 (s, 1H), 6.71 (d, J = 7.9 Hz, 2H), 6.35 (s, 1H), 3.84 (s, 3H). 13C NMR (75 MHz, CDCl3): 157.6, 146.6, 146.4, 146.3, 145.6, 143.7, 137.2, 136.7, 134.9, 131.7, 131.1, 130.7, 130.4, 130.1, 129.5, 129.5, 129.4, 129.3, 129.0, 128.6, 128.4, 127.70, 127.68, 127.6, 127.4, 127.1, 126.72, 126.69, 126.5, 126.1, 125.01, 124.99, 124.8, 124.5, 120.84, 120.82, 119.1, 116.1, 100.6, 84.8, 59.6, 55.3. EI-MS (TOF) m/z (%): 654 (M+, 27), 577 (100), 450 (12), 435 (10), 361 (12). HRMS (EI-TOF) m/z: [M]+ Calcd. for C49H34O2 654.2559; Found 654.2560. 12-methoxy-2-(4-methoxyphenyl)-2-(naphth-1-yl)-8,8-diphenyl2H,8H-naphtho[1,2,3-de]naphtho[1,2-b]pyran 4e. (82 mg, 30% yield). IR (cm−1): 3055, 2951, 1509, 1256. 1H NMR (300 MHz, CDCl3): 8.32 (d, J = 8.4 Hz, 1H), 7.75−7.83 (m, 2H), 7.72 (d, J = 8.0 Hz, 1H), 7.19 (d, J = 8.2 Hz, 1H), 7.49 (m, 2H), 7.41 (d, J = 8.9 Hz, 1H), 7.21−7.39 (m, 9H), 7.16 (t, J = 7.9 Hz, 2H), 7.02−7.13 (m, 2H), 6.97 (m, 3H), 6.75 (m, 5H), 6.38 (s, 1H), 3.86 (s, 3H), 3.79 (s, 3H). 12036

DOI: 10.1021/acs.joc.7b01669 J. Org. Chem. 2017, 82, 12028−12037

Article

The Journal of Organic Chemistry 13

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C NMR (75 MHz, CDCl3): 158.6, 157.4, 146.5, 146.45, 146.4, 143.6, 137.7, 137.4, 136.7, 134.9, 131.8, 131.0, 130.6, 130.4, 130.2, 129.5, 129.4, 129.2, 129.0, 128.8, 128.1, 127.7, 127.6, 127.5, 127.1, 126.7, 126.4, 126.1, 125.0, 124.8, 124.6, 123.8, 120.8, 119.0, 116.1, 113.6, 100.6, 84.4, 59.6, 55.3, 55.2. EI-MS (TOF) m/z (%): 684 (M+, 55), 607 (35), 577 (28), 557 (100), 500 (14), 480 (26), 465 (23), 361 (19), 289 (12). HRMS (EI-TOF) m/z: [M]+ Calcd. for C50H36O3 684.2664; Found 684.2688. Preparation of the Organic−Inorganic Hybrid Films. A solution of 3-(glycidoxypropyl)methyldiethoxysilane (225 mg) and methanol (230 mg) was stirred at room temperature for 20 min and then water (130 mg) and Jeffamine 600 (225 mg) were added. The sol was maintained under stirred for 2 h at room temperature, and then a solution of fused-naphthopyran 4a−e (2 mg) in THF (130 mg) was added and the mixture was stirred vigorously. After 15 min, the sol was deposited in a Teflon dish and cured at 50 °C for 24 h affording a disk with 2 mm thickness.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b01669. 1 H and 13C NMR spectra of all new compounds, with proton and carbon assignments for compounds 4a−e, NMR characterization of the photoproducts P1 and P2, kinetic data and photos of the fused naphthopyran 4b in solution under sunlight (PDF) Movie S1, Solution 1 (AVI) Movie S2, Sunlight sem som (AVI) Movie S3, Sol Gel 1 (AVI)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (P.J.C.) ORCID

Jerome Berthet: 0000-0002-9868-3983 Paulo J. Coelho: 0000-0003-4328-5694 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge FCT (Portugal’s Foundation for Science and Technology) and FEDER for financial support ́ through the research unit Centro de Quimica-Vila Real (UID/ QUI/00616/2013) and Jorge Machado for helping with the synthesis of some of these compounds. The 300 and 500 MHz NMR facilities were funded by the Région Nord-Pas de Calais (France), the Ministère de la Jeunesse de l′Education Nationale et de la Recherche (MJENR), and the Fonds Européens de Développement Régional (FEDER).

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REFERENCES

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DOI: 10.1021/acs.joc.7b01669 J. Org. Chem. 2017, 82, 12028−12037