Asymmetric Hydrogenation of Nonfunctionalized Olefins in Propylene

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Asymmetric Hydrogenation of Nonfunctionalized Olefins in Propylene Carbonate—Kinetic or Thermodynamic Control? Sergey P. Verevkin* and Vladimir N. Emel’yanenko Department of Physical Chemistry, University of Rostock, Dr-Lorenz-Weg 1, 18059 Rostock, Germany

Jerome Bayardon Institut de Chimie Moleculaire (ICMUB, UMR CNRS 5260), University of Burgundy, Dijon 21078, France

Benjamin Sch€affner Evonik Industries AG, Paul-Baumann Straße 1, 45772 Marl, Germany

Wolfgang Baumann and Armin B€orner Leibniz-Institut f€ur Katalyse e.V., A.-Einstein-Strasse 29a, 18059 Rostock, Germany

bS Supporting Information ABSTRACT: Iridium-catalyzed hydrogenations of nonfunctionalized olefins in propylene carbonate as the solvent allow efficient catalysis with much higher enantioselectivities in comparison with dichloromethane which is usually employed for these reactions. Experimental and computational studies of the hydrogenation of 1-methylene-1,2,3,4-tetrahydronaphthalene have been performed to understand the limitation for this reaction.

1. INTRODUCTION Liquid organic carbonates have been identified as alternative solvents in several chemical applications.1,2 First applied as solvent for physical absorption of carbon dioxide in natural gas streams, extractions, and as nonaqueous solvent in electrochemical applications, they were recently used as effective reaction media for catalysis.1,2 Especially alkylene carbonates have perfect properties to act as a so-called “green” solvent. Cyclic carbonates like propylene carbonate (4-methyl-1,3-dioxolan-2-one = PC) exhibit excellent solvency properties combined with environmentally friendly physical data (high boiling point, inflammable, low toxicity, biodegradable, odorless, noncorrosive). They can be used as 00 safe00 and environmentally friendly reaction media replacing harsh solvents such as methylene chloride, acetone, aromatic solvents, and other so-called VOCs (volatile organic compound).3 Additionally, noncyclic organic carbonates are useful synthetic compounds to prevent the use of toxic phosgene in lab-scale reactions.4 Organic carbonates are readily available from several solvent manufacturers and reach a worldwide annual production of 0.81 Mt. Huntsman produces its carbonates via alkyl epoxides in three separate manufacturing facilities for ethylene carbonate, PC, and butylene carbonate.5 BASF is using the environmentally friendly HPPO process to produce propyleneoxide from propene with H2O2.6 However, especially noncyclic carbonates are still produced in the traditional reaction of toxic phosgene and methanol.1 Other synthetic pathways are still in research and not industrially applied.7 While ethylene carbonate is solid at room temperature, propylene and butylene r 2011 American Chemical Society

carbonate are fairly viscous liquids and therefore suitable to act as polar reaction media. Propylene carbonate has been shown to be a perfect solvent in the asymmetric rhodium-catalyzed hydrogenations of functionalized olefins like methyl N-acetamidoacrylate, methyl α-(Z)-N-acetamidocinnamate, lactic acid precursors, and terminal alkenes.810 Furthermore, the kinetic behavior of the transformation of diolefinic Rh-precatalysts into the catalytically active species in PC in comparison to other solvents was investigated.11 In our recent publications we have demonstrated significant advantages of PC in the asymmetric hydrogenations with chiral Ir-complexes,12 as well as for palladium-catalyzed substitution reactions.13 Kinetic aspects of the hydroformylation of olefins in the multiphase systems and acceleration effect of PC were also intensively studied by Behr et al.14,15 They have shown very high efficiency when using PC; for example, the isomerizing hydroformylation of trans-4-octene in a two-phase solvent system of PC and dodecane lead to very high conversions of 95% of the olefin.15 Our previous studies have focused on the physicochemical properties of alkylene1618 and alkyl carbonates.19,20 In the current study our aim was to study the thermodynamic aspects of the asymmetric hydrogenation of 1-methylene-1,2,3,4-tetrahydronaphthalene (1) in PC with [Ir(cod)L]BArF (BArF = B(C6H3(CF3)2)4) (see Figure 1). Received: February 7, 2011 Accepted: November 19, 2011 Revised: November 18, 2011 Published: November 20, 2011 126

dx.doi.org/10.1021/ie200269q | Ind. Eng. Chem. Res. 2012, 51, 126–132

Industrial & Engineering Chemistry Research

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Figure 2. Compounds under study: 1-methylene-1,2,3,4-tetrahydronaphthalene (1) and 4-methyl-1,2-dihydronaphthalene (2), and product 1-methyl-1,2,3,4-tetrahydronaphthalene (3).

n-hexane as eluent. Colorless oil; yield = 80%; Rf = 0.48 (nhexane). 1H NMR (300 MHz): δ = 7.627.65 (m, 1H; ArH), 7.107.17 (m, 3H; ArH), 5.46 (d, 2J(H,H) = 1.2 Hz, 1H; C = CH2), 4.94 (d, 2J(H,H) = 1.2 Hz, 1H; C = CH2), 2.84 (t, 3J(H,H) = 6.3 Hz, 2H; CH2), 2.512.56 (m, 2H; CH2), 1.861.91 (m, 2H, CH2). 4-Methyl-1,2-dihydronaphthalene (2). The compounds was synthesized in two steps using the established procedures.27,28 Colorless oil; Rf = 0.32 (n-hexane). 1H NMR (300 MHz): δ = 7.127.30 (m, 4H; ArH), 5.895.90 (m, 1H; C = CH), 2.752.84 (m, 2H; CH2), 2.292.33 (m, 2H; CH2), 2.27 (s, 3H, CH3). Purities of the compounds were proven using a gas chromatograph (GC) with a flame ionization detector. A HP-5 capillary column (stationary phase cross-linked 5% PH ME silicone) was used in all our experiments. The column was 30 m long, 0.32 mm inside diameter, and had a film thickness of 0.25 μm. The flow rate of the carrier gas (nitrogen) was maintained at 7.2 dm3 3 h1. The starting temperature for the GC was T = 323 K for the first 180 s followed by heating to T = 523 K at a rate of 10 K 3 min1. No impurities more than 0.02 mass percent were detected in all samples used in this work. Hydrogenation of 1-Methylene-1,2,3,4-tetrahydronaphthalene (1) with the Iridium Catalyst. Hydrogenation experiments were performed in an autoclave with 0.004 mmol of [Ir(COD)L]BArF and 0.4 mmol of the prochiral olefin in 8 mL of solvent at 298 K under atmospheric or enhanced pressure of H2. After completion of the reaction, the solvent was evaporated and the residue analyzed. With PC as solvent, after the reaction the solution was extracted with a mixture of toluene/n-hexane (1/3), then the solvent was evaporated and the residue was analyzed. Conversion and degree of isomerization/reduction of substrate 1 were determined by NMR or GC. Enantiomeric excess of (3) was determined by chiral GC (50 m Lipodex E, 333 K). Labeling experiments were performed by conduction the reactions with D2 in CH2Cl2 as well as in PC. The deuterium distribution in the 1-methyltetraline was investigated by NMR spectroscopy. Vapor Pressure Measurements. Vapor pressures of 1-methylene-1,2,3,4-tetrahydronaphthalene (1) and 4-methyl-1,2-dihydronaphthalene (2) were determined using the method of transpiration29,30 in a saturated nitrogen stream. About 0.5 g of the sample was mixed with glass beads and placed in a thermostatted U-shaped tube having a length of 20 cm and a diameter of 0.5 cm. Glass beads with a diameter of the glass spheres of 1 mm provide a surface large enough for rapid vaporliquid equilibration. At a constant temperature ((0.1 K), a nitrogen stream was passed through the U-tube and the transported amount of material was collected in a cooling trap. The flow rate of the nitrogen stream was measured using a soap bubble flow meter and was optimized in order to reach the saturation equilibrium of the transporting gas at each temperature under study. The amount of condensed substance was determined by GC analysis

Figure 1. Hydrogenation of 1-methylene-1,2,3,4-tetrahydronaphthalene (1).

In our recent study we have observed that with PC as solvent much higher enantioselectivities can be achieved than with CH2Cl2 which is usually employed for this transformation.12 We have concluded from the kinetic study that in CH2Cl2 the isomerization of 1 into the internal olefin 2 is much faster than in PC.12 Since with the same chiral Ir-catalyst in hand 2 is converted into the product 3 with the opposite configuration, for example, (S)-3, in comparison to substrate 1, which gives (R)-3, the lowering of the ee-values with progressing isomerization becomes obvious. One of the possible explanations for such a behavior could be a competition between the isomerization 1 T 2 and hydrogenation rates. Thus, it is important to clarify, whether the reactions on Figure 1 occur under kinetic or thermodynamic control? Similar temperature dependent studies of the network of hydrogenation and isomerization reactions but on geraniol as the substrate have been performed by Blackmond and coworkers.21,22 They also observed that competition between the isomerization and hydrogenation rates plays a role in dictating enantioselectivity in asymmetric hydrogenation of the geraniol. These results have emphasized the importance of monitoring reaction progress whenever the potential for competitive reactions exists.21 To understand reasons for different enantioselectivity observed12 in PC and methylene chloride, experimental and computational studies of thermodynamic properties of both isomers 1-methylene-1,2,3,4-tetrahydronaphthalene (1) and 4-methyl1,2-dihydronaphthalene (2) have been performed in this study. These results could give hints whether the reaction occurs under kinetic or thermodynamic control. This paper also contributes to our primary interest in the application of thermochemistry2326 for providing the basic information required in chemical-process and chemical-product design.

2. EXPERIMENTAL SECTION Materials. Samples of 1-methylene-1,2,3,4-tetrahydronaphthalene and 4-methyl-1,2-dihydronaphthalene were obtained according to the following experimental procedures. 1-Methylene-1,2,3,4-tetrahydronaphatalene (1). To a solution of tetralone (15.1 mmol) in dry diethylether (120 mL) was added under argon methyltriphenylphosphonium bromide (5.35 g, 15.0 mmol) and tert-butoxide potassium (1.68 g, 15.0 mmol). The mixture was stirred at room temperature overnight then the solvent was removed under vacuo. n-Hexane was added, and the solution was filtered through a path of Celite. The solvent was removed and the residue purified by flash chromatography using 127

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Figure 3. Conversion of 1 and ratio of isomer 2 and product 3.12

Figure 4. Enantioselectivities of the hydrogenation product 3 dependent on solvent and hydrogen pressure used.12

using an external standard (hydrocarbon n-decane). The saturation vapor pressure pisat at each temperature Ti was calculated from the amount of the product collected within a definite period of time. Assuming that Dalto ns law of partial pressures applied to the nitrogen stream saturated with the substance i of interest is valid, values of pisat were calculated with equation: pi sat ¼ mi RTa =VMi ;

V ¼ VN2 þ Vi ;

ðVN2 . Vi Þ

reproducibility of GC measurements. Experimental results are collected in Table S1 (Supportimg Information). Computations. Standard ab initio molecular orbital calculations were performed with the Gaussian 03 Rev.04 series of programs.31 Energies were obtained at the DFT (B3LYP/ 6-311G(d,p))32 and the G3MP233 level of theory. No corrections for internal rotors have been taken into account. The enthalpy values of at T = 298 K were evaluated according to standard thermodynamic procedures.34

ð1Þ

where R = 8.314472 J 3 K1 3 mol1; mi is the mass of the transported compound, Mi is the molar mass of the compound, and Vi is its volume contribution to the gaseous phase. VN2 is the volume of the carrier gas and Ta is the temperature of the soap bubble meter. The accuracy of the volume VN2 measurements from the flow rate was assessed to be ((0.001 dm3). The volume of the carrier gas VN2 was determined from the flow rate and the time measurement. It was established29 that the total uncertainty of the data for this experimental technique was within the range from 1 to 3% with the main source of errors attributed to the

3. RESULTS AND DISCUSSION Asymmetric Hydrogenation of 1-Methylene-1,2,3,4-tetrahydronaphthalene (1). In our previous study of the asymmetric

hydrogenation of nonfunctionalized olefins in PC,12 we reduced 1-methylene-1,2,3,4-tetrahydronaphthalene (1) under different conditions (see Figure 3). The reactions were performed at normal and high pressure and the results were compared with those obtained in dichloromethane (DCM). The results are summarized in Figures 3 and 4.

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Table 1. Results of the Ir-Catalyzed Asymmetric Hydrogenation of 1-Methylene-1,2,3,4-tetrahydronaphthalene (1) in Propylene Carbonate (PC) with [Ir(cod)oxazolidinone phosphinite]B(C6H3(CF3)2)4 compound

H2 (bar)

time (h)

convn (%)

yield 2/3 (%)

ee (%)

Solvent = PC 1

1

20

74

63/37

73.2 (R)

1

50

4

100

13/87

81.3 (R)

1

50

8

100

4/96

82.1 (R)

1

85

4

100

5/95

82.1 (R)

3/97

82.4 (R)

1

100

4

100

2

1

24

12

n.d.a

5.9 (S)

2

50

4

24

n.d.a

35.4 (S)

1

1

3

100

71/29

46.3 (R)

1

50

3

100

0/100

16.9 (R)

2

50

3

100

Figure 6. Labeling experiments with 1-methylene-1,2,3,4-tetrahydronaphthalene with D2.

enantiomeric excess of 59.5% in favor of the (S)-enantiomer. Surprisingly, in PC only 24% conversion was obtained after 4 h, the enantioselectivity being 35.4% ee (S) in this case (for details see Table 1). Under these conditions, the reduction of the internal double bond of compound 2 is slower in PC than in DCM. At this point, the reason for the slower conversion of compound 2 in PC remains unclear. On the other hand, in the absence of hydrogen, compound 1 was completely transformed within 10 min into the isomer 2 in DCM, whereas in PC, only 39% of 2 was formed within 1 h. Following, the isomerization reaction itself is significantly faster in DCM than in PC. This result gives first evidence, that the asymmetric hydrogenation is likely kinetically controlled, provided that the thermodynamic stability of 1 is less than those of 2. Furthermore it should be mentioned, that in the isomerizationhydrogenation network it is possible that (R)-3 is produced by the concomitant hydrogenation of 2 (Figure 5). Thus, the reaction rate (k2) could be drastically lowered in comparison to k1. This effect was also described by Blackmond and co-workers in the hydrogenation of geraniol.21,22 A hint for the same mechanism with 1 is given by the substantial change in the stereoselectivity with increasing the hydrogen pressure. When the pressure in PC was increased from 1 over 50 to 100 bar, the enantioselectivity increased from 73.2 to 82.4% (R) within 4 h (see Table 1). These results nicely demonstrate that the increased driving force for the hydrogenation (k1) is directly supported by increased hydrogen pressure relative to the isomerization rate (kiso). However, this mechanism cannot be used in similar manner for the hydrogenation in DCM, since a decrease in the stereoselectivity was achieved while increasing the hydrogen pressure (from 16.9% (R) for 50 bar to 46.3% (R) for 1 bar hydrogen pressure in 3 h). But since it is known that isomerization to 2 took place within 10 min it can be expected that the hydrogenation to 3 occurs via k3 and k4.12 Thus, the equilibrium of the reaction 1 T 2 in DCM is completely shifted to 2 and the consequent hydrogenation pf the isomer 2 was responsible for the observed low enantioselectivity in DCM. Therefore we focused our further investigations on the reaction in PC. Labeling Experiments of 1-Methylene-1,2,3,4-tetrahydronaphthalene (1) with D2. More detailed understanding of the mechanisms of the hydrogenationisomerization network presented on the Figure 1 provided the D2 labeling experiments with the isomer 1 (see Figure 6). In DCM most, but not all of the deuterium was equally distributed to positions trans-1 and trans2, in accord with the suggestion that the product is formed predominantly via the cyclic alkene. In PC, distribution was more widespread (see Table 2). In both solvents, not only the two

Solvent = DCM

a

n.d.a

59.5 (S)

n.d. = not determined.

Figure 5. Possible isomerization and hydrogenation pathways of isomeric olefins 1 and 2.

It was shown that hydrogenation of 1 in DCM or PC led to a mixture of products 2 and 3 with conversion of 74% in PC and full conversion in DCM with an enantiomeric excess for compound 3 of 46.3% in DCM and 73.2% in PC. Under these conditions, the use of DCM rather than PC allows the acquisition of a better ratio of 2/3 in favor of 3. To increase the proportion of 3, an increase of pressure from 1 to 50 bar in DCM or from 1 up to 100 bar in PC was necessary. Thus, good to excellent ratios of 2/3 were obtained (13/87 at 50 bar, 5/95 at 85 bar, 3/97 at 100 bar in PC and 0/100 at 50 bar in DCM) according to the results given in Table 1. Superior enantioselectivities were obtained in PC (up to 82.4% ee (R) at 100 bar H2). In this case, the use of PC is the precondition to obtain high enantioselectivities. As it is clearly seen, at 50 bar, ee-values obtained in PC are superior to those noted in DCM (81.3 and 16.9%, respectively). An increase of the H2-pressure from 50 to 85 and 100 bar improved further the ee-values in PC (81.3, 82.1 and 82.4%, respectively). To distinguish between thermodynamic and kinetic control of the process presented on Figure 1, we have carried out some hydrogenations of compound 2 in PC and in DCM at 50 bar to determine the absolute configuration of the obtained product 3. After three hours, full conversion was obtained in DCM with an 129



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Table 2. Spectra of 1-Methyl-1,2,3,4-tetrahydronaphthalene Obtained by Hydrogenation of 1-Methylene-1,2,3,4-tetrahydronaphthalene (1) with D2 methyl 1.37 ppm

1 2.98 ppm

cis-2 1.61 ppm

trans-2 2.00 ppm

reaction in DCM

a

H NMR

0.95

0.24

0.94

0.34

reaction in PC

H NMRb H NMRa

0.43 0.83

1.00 0.50

0.13 0.48

0.97 0.46

H NMRb

0.93

1.00

1.07

0.95

position

a

H NMR: signal intensity ratio deuterated compound/nondeuterated compound. b H NMR: relative signal intensities scaled to signal of 1-H. Solvent CDCl3.

Table 3. Enthalpies and Gibbs Energies of the Isomerisation Reaction 1 S 2 at 298 and 373 K in the Gas Phase (in kJ 3 mol1) G3MP2 temp (K)

Figure 7. Possible isomeric structures of naphthalene derivatives and their relative (to isomer 1) energies at B3LYP/6-311G(d,p) level.

dideuterated products (Figure 6) expected from direct hydrogenation ensued. For example, we observed significant deuterium incorporation in the cis-2 position both by 1H and 2H NMR spectroscopy. Table 2 shows the relative incorporation of deuterium into the olefin. The relative values, scaled to the signal of the proton at the C1 position, present the distribution between the carbon atoms C1C4 (see Figure 6). This is not explicable by product generation from either starting material. Close inspection of 13 C NMR spectra35 revealed complicated signal patterns due to complex isotopomer mixtures. Therefore, it is likely that reversibility of steps within the catalytic cycle36 may lead to generation of HD and subsequent deuterium scrambling. This prevents clear-cut mechanistic interpretation of the observations. Computational and Thermochemical Study of Isomeric Olefins (1) and (2). The experimental results given in Table 1 have suggested that the asymmetric hydrogenation is most likely kinetically controlled, provided that thermodynamic stability of 1 is less than those of 2. More definite answer could be obtained from thermochemical study of the isomers 1 and 2. Already a quick appraisal of the thermodynamic stability of the 1 and 2 with the help of DFT-calculations (B3LYP/6-311G(d,p) level) at 298 K revealed (see Figure 7), that among possible isomeric structures 1, 2, 6, and 7, the isomeric structure 2 is the most stable one, followed by isomers 7 and 1, while isomer 6 is the least stable. Thus, we have studied the experimentally existing isomers 1 and 2 more carefully using G3MP2 and B3LYP/6-311G(d,p) methods. Results from quantum-mechanical (QM) calculations are collected in Table 3 and Tables S2S4 (in the Supporting Information). Results from QM calculations for the Gibbs energies ΔrG of the isomerization reaction 1 S 2 allowed assessment of the thermodynamic equilibrium constant KP of this reaction in the gaseous phase according to the general equation: Δr G ¼ RT ln KP

ΔrH

ΔrG

B3LYP/6-311G(d,p) ΔrH

ΔrG

298

15.2

15.9

17.8

18.5

373

14.4

15.4

17.6

18.7

in the present study catalytic reactions occur in the liquid phase, the value of the equilibrium constant in the liquid phase, Ka, is required: Ka ¼ KP ðp1 =p2 Þ

ð3Þ

where p1 and p2 are an appropriate saturation vapor pressures of isomers 1 and 2. The latter vapor pressures have been measured using the transpiration method in the temperature range of 293359 K (see Supporting Information, Table S1). From this results the vapor pressures p1 = 13.6 Pa and p2 = 12.2 Pa at 298 K have been obtained and used for calculation of Ka = 682 in the liquid phase. It is now apparent that equilibrium of the reaction 1 S 2 in the liquid phase is also completely shifted to the product 2, however, the impact of the temperature on to the equilibrium should be explored. For this purpose the QM calculations of the reaction 1 S 2 have been performed at 373 K (see Table 3). Together with the results for vapor pressures p1 = 1442 Pa and p2 = 1201 Pa at 373 K (obtained using data from Supporting Information, Table S1) the values for KP =143 in the gaseous phase and Ka = 160 in the liquid phase have been calculated. The same trend has been obtained from calculations with the B3LYP/ 6-311G(d,p) method. As can be seen from these calculation, the isomerization 1 S 2 displays a strong temperature dependency, thus elevated temperatures could be also recommended in order to avoid formation of the side product 2 in the liquid phase. According to the experimental and computational studies, now we are able to conclude definitely that the asymmetric hydrogenation of 1 is kinetically controlled under our conditions. It is now apparent, that the isomerization of the external olefin of compound 1 to the most stable internal isomer 2, which occurs during the hydrogenation reaction, is faster in DCM than in PC. Hydrogenation of these two prochiral isomeric olefins 1 and 2 gives corresponding products with opposite absolute configuration; 1 gives the (R) enantiomer, whereas 2 gives the (S) enantiomer (Figure 1). However, the QM calculations in this work were based only on the energy levels of the starting material and product. Some specific effects during the formation of the transition state during the catalysis could play an additional role. For example, several catalytic steps were observed in studies of

ð2Þ

Using ΔrG = 15.9 kJ 3 mol1 from G3MP2 method (see Table 3) the value for KP = 612 has been calculated. This result suggested that in the gas phase during isomerization 1 S 2 an equilibrium is completely shifted to the side product 2. Because 130



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(10) Mazuela, J.; Verendel, J. J.; Coll, M; Sch€affner, B.; B€orner, A.; Anderson, P. G.; Pamies, O.; Dieguez, M. Iridium PhosphiteOxazoline Catalysts for the Highly Enantioselective Hydrogenation of Terminal Alkenes. J. Am. Chem. Soc. 2009, 131, 12344–12353. (11) Preetz, A.; Drexler, H.-J.; Fischer, C.; Dai, Z.; B€orner, A.; Baumann, W.; Spannenberg, A.; Thede, R.; Heller, D. Rhodium complex catalyzed asymmetric hydrogenation—Transfer of pre-catalysts into active species. Chem.—Eur. J. 2008, 14, 1445–1451. (12) Bayardon, J.; Holz, J.; Sch€affner, B.; Andrushko, V.; Verevkin, S.; Preetz, A.; B€orner, A. Propylene carbonate as a solvent for asymmetric hydrogenations. Angew. Chem., Int. Ed. 2007, 46, 5971–5974. (13) Sch€affner, B.; Holz, J.; Verevkin, S. P.; B€orner, A. Organic carbonates as alternative solvent for palladium-catalyzed substitution reactions. ChemSusChem 2008, 1, 349–353. (14) Behr, A.; Obst, D.; Schulte, C. Process concepts for the transition metal catalyzed syntheses of formic acid and dimethylformamide based on carbon dioxide. Chem. Eng. Technol. 2004, 76, 904–910. (15) Behr, A.; Obst, D.; Turkowski, B. Isomerizing hydroformylation of trans-4-octene to n-nonanal in multiphase systems: Acceleration effect of propylene carbonate. J. Mol. Catal. A 2005, 226, 215–219. (16) Verevkin, S. P.; Toktonov, A. V.; Chernyak, Y.; Sch€affner, B.; B€orner, A. Vapour Pressure and Enthalpy of Vaporization of Cyclic Alkylene Carbonates. Fluid Phase Equilib. 2008, 268, 1–6. (17) Verevkin, S. P; Emel’yanenko, V. N.; Toktonov, A. V.; Chernyak, Y.; Sch€affner, B.; B€orner, A. Cyclic alkylene carbonates. Experiment and first principles calculations for prediction of thermochemical properties. J. Chem. Thermodyn. 2008, 40, 1428–1432. (18) Kumezan, J.; Tuma, D.; Verevkin, S. P.; Maurer, G. The solubility of hydrogen in the cyclic alkylene ester 1,2-butylene carbonate. J. Chem. Eng. Data 2008, 53, 2844–2850. (19) Kozlova, S. A.; Emel’yanenko, V. N.; Georgieva, M.; Verevkin, S. P.; Chernyak, Y.; Sch€affner, B.; B€orner, A. Vapour pressure and enthalpy of vaporization of aliphatic dialkyl carbonates. J. Chem. Thermodyn. 2008, 40, 1136–1140. (20) Verevkin, S. P.; Emel’yanenko, V. N.; Kozlova, S. A. Organic carbonates: Experiment and ab initio calculations for prediction of thermochemical properties. J. Phys. Chem. A 2008, 112, 10667–10673. (21) Sun, Y.; LeBlond, C.; Wang, J.; Blackmond, D. G. Observation of a [RuCl2((S)-()-tol-binap)]2N((C2H5)3-catalyzed isomerization hydrogenation network. J. Am. Chem. Soc. 1995, 117, 12647–12648. (22) Sun, Y.; Wang, J.; LeBlond, C.; Landau, R. N.; Laquidara, J.; Sowa, J. R., Jr.; Blackmond, D. G. Kinetic influences on enantioselectivity in asymmetric catalytic hydrogenation. J. Mol. Catal. A: Chem 1997, 115, 495–502. (23) Verevkin, S. P.; Emel’yanenko, V. N.; Toktonov, A. V.; Leolko, A.; Duwensee, J.; Kragl, U.; Sarge, S. M. Thermochemical and ab initio studies of biodiesel fuel surrogates: 1,2,3-Propanetriol triacetate, 1,2ethanediol diacetate, and 1,2-ethanediol monoacetate. Ind. Eng. Chem. Res. 2009, 48, 7388–7399. (24) Verevkin, S. P.; Emel’yanenko, V. N.; Toktonov, A. V.; Goodrich, P.; Hardacre, C. Thermochemistry of ionic liquid-catalysed reactions. Theoretical and experimental study of the Beckmann rearrangement Kinetic or thermodynamic control? Ind. Eng. Chem. Res. 2009, 48, 9809–9816. (25) Cammenga, H. K.; Emel’yanenko, V. N.; Verevkin, S. P. Reinvestigation and data assessment of the isomerization and 2,20 -cyclization of stilbenes and azobenzenes. Ind. Eng. Chem. Res. 2009, 48, 10120–10128. (26) Verevkin, S. P.; Emel’yanenko, V. N.; Stepurko, E. N.; Ralys, R. V.; Zaitsau, D. H.; Stark, A. Biomass-derived platform chemicals: Thermodynamic studies on the conversion of 5-hydroxymethylfurfural into bulk intermediates. Ind. Eng. Chem. Res. 2009, 48, 10087–10093. (27) Noji, M.; Ohno, T.; Fuji, K.; Futaba, N.; Tajima, H.; Ishii, K. Secondary benzylation using benzyl alcohols catalyzed by lanthanoid, scandium, and hafnium triflate. J. Org. Chem. 2003, 68, 9340–9347. (28) Firaouzabadi, H.; Iranpoor, N.; Hazarkhani, H.; Karimi, B. Silica chloride (SiO2—Cl) and trimethylsilyl chloride (TMSCl) promote facile and efficient dehydration of tertiary alcohols. Synth. Commun. 2003, 33, 3653–3660.

the transition metal catalyzed hydrogenation by Blackmond et al.22 A later publication by Heller and co-workers also described a complex relationship between hydrogen pressure, reaction pathway, and the enantioselectivity.37 In contrast to the results of Blackmond et al.,21,22 Boudart et al.38 discussed the principles of the kinetic coupling in catalytic cycles with many elementary steps to reduce the number of equations via quasiequilibrated steps.38 The later results were based on the work of Halpern who suggested the majorminor principle in contrast to the key-lock theory.39,40 Thus, more detailed studies of the mechanisms of the asymmetric hydrogenation of olefins have to be performed. Regardless, the results presented in this study together with our previous work have opened a new window for successful application of alkylene carbonates as effective and selective solvents for chemical reactions.

’ ASSOCIATED CONTENT

bS

Supporting Information. Vapor pressures and geometrical parameters of olefins 1 and 2 (Tables S1S3), total energies at 0 K and enthalpies at 298 K (in Hartree) of the molecules studied in this work (Table S4). This material is available free of charge via the Internet at http://pubs.acs.org.

’ AUTHOR INFORMATION Corresponding Author

*Tel.: +49-381-498-6508. Fax: +49-381-498-6524. E-mail: sergey. [email protected].

’ ACKNOWLEDGMENT This work has been supported by Research Training Group “New Methods for Sustainability in Catalysis and Technique” (D.F.G.). Special thanks to Silke Erfle for performing hydrogen labeling experiments. ’ REFERENCES (1) Sch€affner, B.; Sch€affner, F.; Verevkin, S. P.; B€orner, A. Organic carbonates as solvents in synthesis and catalysis. Chem. Rev. 2010, 110, 4551–4581. (2) Sch€affner, B.; Verevkin, V. P.; B€orner, A. Gr€une l€osungsmittel f€ur synthese und katalyse: Organische carbonate. Chem. Unserer Zeit 2009, 43, 12–21. (3) In 2005 BASF replaced the more toxic cresol by PC after an ecoefficiency study of both solvents. (see Sustainable Development by BASF http://www.corporate.basf.com/en/sustainability. URL accessed February 07, 2011). (4) Shaikh, A.-A. G.; Sivaram, S. Organic Carbonates. Chem. Rev. 1996, 96, 951–976. (5) Performance Products, http://www.huntsman.com. URL accessed February 07, 2011. (6) New BASF and Dow HPPO Plant in Antwerp Completes StartUp Phase, http://www.basf.com/group/pressrelease/P-09-154. URL accessed February 07, 2011. (7) Sakakura, T.; Choi, J.-C.; Yasuda, H. Transformation of Carbon Dioxide. Chem. Rev. 2007, 107, 2365–2387. (8) Sch€affner, B.; Holz, J.; Verevkin, S. P.; B€orner, A. Rhodiumcatalyzed asymmetric hydrogenation with self-assembling catalysts in propylene carbonate. Tetrahedron Lett. 2008, 49, 768–771. (9) Sch€affner, B.; Andrushko, V.; Holz, J.; Verevkin, S. P.; B€orner, A. Rh-catalyzed asymmetric hydrogenation of unsaturated lactate precursors in propylene carbonate. ChemSusChem 2008, 1, 934–940. 131



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Asymmetric Hydrogenation of Nonfunctionalized Olefins in Propylene

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