Ind. Eng. Chem. Prod. Res. Dev. 1983,22, 118-120
118
Darzens Glycidic Ester Condensation of Benzaldehyde in Solid-Liquid Two-Phase System Chlkal Klmura, Kageakl Kashlwaya, Kolchl Mural, and Hlroyukl Katada Department of Fuel Chemistry, Mining College, Akita University, Akita 0 10, Japan
The Darzens glycidic ester condensation was undertaken to prepare ethyl 0-phenylglycidate from benzaldehyde in a solld-liquid two-phase system at higher temperature than 100 OC employing anhydrous potassium carbonate as a condensing agent. I t has been found that the reaction is accelerated considerably by a catalyst such as crown ether and the glycklic ester can be obtained in excellent yield. Efforts have been made to reveal the effects of reaction conditions, such as the molar ratio of reactants and the amount of catatyst, condensing agent, or solvent, on the yield and the cis/trans isomer ratio of the product. Thus, the present procedure was found to present a valuable improvement in the Darzens condensation of benzaldehyde, but preliminary experiments revealed that a ketone such as acetophenone took part in the reaction with a poor yield ( DC-18-C-6 > DB-18-C-6 > Bu4P+Br- > PhCH,N+Et,Br-. The two crown ethers, 18-C-6 and DC18-C-6, exhibited a significant catalytic activity and a maximum yields of 92% and 84%, respectively, were obtained in about 4 h in contrast to the corresponding yield of 48% in the case of no catalyst. DB-18-C-6, however, showed a smaller catalytic effect to obtain the maximum yield in 7 h. The phosphonium salt exerted catalytic activity only sightly, and the ammonium salt negatively with
0196-4321/83/1222-01 18$01.50/0 0 1983 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 1, 1983 119 0.5 mol
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Figure 4. Effect of amount of C1CH2COOEt. Reaction conditions: PhCHO, 0.1 mol; KzC03, 0.2 mol; 18-C-6, 1 mmol; solvent, 30 mL; temperature, 130 "C.
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Figure 2. Effect of amount of catalyst (18-C-6). Reaction conditions: PhCHO, 0.1 mol; C1CH2COOEt,0.15 mol; KzC03,0.12 mol; solvent, 30 mL; temperature, 130 OC.
Figure 5. Effect of amount of K2C03. Reaction conditions: PhCHO, 0.1 mol; ClCHzCOOEt, 0.15 mol; 18-C-6,1 mmol; solvent, 30 mL; temperature, 130 "C. 100,-
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Figure 3. Effect of reaction temperature. Reaction conditions: PhCHO, 0.1 mol; C1CH2COOEt,0.5 mol; KzCO3, 0.2 mol; 18-C-6, 1 mmol; solvent, 30 mL.
Figure 6. Effect of concentration. Reaction conditions: PhCHO, 0.1 mol; CICHzCOOEt,0.15 mol; K2C03,0.12 mol; 18-C-6, 1 mmol; temperature, 130 OC.
a poorer yield than no catalyst, partially because of its instability a t higher temperature. As shown in Figure 7, the cis/trans isomer ratio varied greatly with catalyst and decreased in the order of DC-18-C-6 (0.44),1842-6 (0.33), DB-184-6 (0.19), and Bu4P+Br-(0.10). A t the initial stage of the reaction the ammonium salt showed a higher isomer ratio which, then decreased rapidly with time, suggesting the decomposition of the catalyst. Amount of Catalyst. In accord with anticipation, the use of a larger amount of catalyst caused an increasing
acceleration of the reaction as shown in Figure 2. When 1 mol % catalyst against benzaldehyde was employed, it took 5 h to attain a maximum yield, but 2 h was found to be sufficient in the case of 4 mol % catalyst, and the yield decreased rapidly afterwards with an increasing cisltrans isomer ratio (Figure 7). This tendency suggests that the trans isomer undergoes the side reaction in preference to the cis isomer, which remains virtually unchanged as shown in Figure 2. Similar reaction features are also observed in other cases demonstrated in Figures 4, 5, and 6.
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 1, 1983
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Reaction Temperature. The reaction was carried out at 100 and 130 "C. From the results illustrated graphically in Figure 3, it is easily understood that the reaction should be performed a t higher than 100 "C. At 130 "C, near the boiling point of o-xylene, a satisfactory yield was obtained in a short reaction time and the cis/trans isomer ratio was found to be smaller (0.33) than a t 100 "C (0.45) as shown in Figure 7. Amount of Ethyl Chloroacetate. In order to examine the effect of the molar ratio of reactants, the reaction was carried out employing ethyl chloroacetate in excess against
benzaldehyde (Figure 4). In the case of a 1-51molar ratio the reaction proceeded to a maximum yield in about 3 h, but the yield began to decrease thereafter as stated above. In the case of a 3:l and a 5:l molar ratio, it took a longer time to reach a maximum yield than in the case of the 151. The cis/trans isomer ratio showed a nearly equal value (0.26) in the cases of the 1.51 and the 3:l molar ratio, and a larger value (0.33) in the case of the 5:l molar ratio (Figure 8). Amount of Potassium Carbonate. In Figure 5 are represented the experimental results of the reaction carried out employing a 1.2-3-fold amount of K2COBagainst benzaldehyde. It can be seen from the results that a better yield is obtained with an increasing amount of the base (Figure 5), but the cie/trans isomer ratio remains nearly unchanged (0.26) as shown in Figure 8. Concentration. The reaction was conducted using 0.1 mol of benzaldehyde in 10 or 30 mL of the solvent (Figure 6). The experimental results showed that the amount of solvent exerts a significant influence on the reaction rate and the product. In the case of 10 mL of the solvent the reaction proceeded rapidly to a maximum yield in about 1.5 h contrary to 5 h in the case of 30 mL (Figure 6). The cis/trans isomer ratio was also influenced by the amount of solvent, showing values of 0.42 in the former case and 0.26 in the latter case (Figure 8). Conclusion In this investigation it has been confirmed that the solid-liquid two-phase procedure is a superior method for the preparation of ethyl p-phenylglycidate to the conventional method, offering some advantages such as high yield, large reaction rate, and elimination of hazardous, expensive reactants. Also, the stereoisomer ratio of the product was found to vary with various reaction factors such as catalyst, solvent, temperature, and the molar ratio of reactants. In the application of the two-phase system it is considered to be essential that an optimum reaction time should be selected in order to avoid the decrease of the yield due to the side reaction of the product. At the same time, it seems advisable to refer to the limited applicability of this method in the Darzens reaction. For instance, preliminary experiments revealed that acetophenone was subjected to similar experiments, but the yield of the resulting glycidic ester never went above 25%.
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Registry No. &-Ethyl 3-phenyloxiranecarboxylate,2272-49-3; trans-ethyl 3-phenyloxiranecarboxylate,2272-55-1; ethyl 3methyl-3-phenyloxiranecarboxylate, 77-83-8; acetophenone, 9886-2; ClCH,COOEt, 105-39-5; PhCHO, 100-52-7;K&03,584-08-7; Bu4P+Br-, 3115-68-2; PhCH2N+Et3Br; 5197-95-5; DB-18-C-6, 14187-32-7; DC-18-C-6, 16069-36-6; 1 8 4 - 6 , 17455-13-9.
Literature Cited Bachelor, F. W.; Bansal, R. K. J. Org. Chem. 1969, 3 4 , 3600. Ballester, M. Chem. Rev. 1955, 5 5 , 283. Fedorynski, M.; Wojeclechowskl, K.; Matacz, 2.; Makosza, M. J. Org. Chem. 1970, 43, 4682. House, H. 0. "Modern Synthetic Reactions", 2nd ed.: W. A. Benjamin, Inc.; Menlo Park, 1972; p 666. Newman, M. S.; Magerleln, B. J. Org. React. 1949, 5 , 413. Seyden-Penne, J.; Roux-Schmitt, M. C.; Roux, A. Tetrahedron 1970, 26, 2649. Valente. V. R.; Wolfhagen, J. L. J . Org. Chem. 1966, 31, 2509.
Received for review April 8, 1982 Accepted September 13, 1982
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