Ethyl benzoylformate hydrogenation

Fig. 7.14 Influence of the mass of modifier in the semibatch reactor in ethyl benzoylformate hydrogenation on 5 wt% Pt/Al203 in hexane/2-propanol solvent at 25°C, pH2 = latm. (From G. Martin, P. Maki-Arvela, J. Warna, K. Fionkala, D.Yu. Murzin, T. Salmi, ind. Eng. Chem. Res. 53 (2014) 11945-11953. Copyright 2014 American Chemical Society).

Table 41.14 Rhodi um-catalyzed hydrogenation of acetophenone (A) and ethyl benzoylformate (B) [105].

Scheme 3.10 Asymmetric hydrogenation of ethyl benzoylformate with a rhodacarborane catalyst...

Reduction of a-keto esters. The reduction of a-keto esters by this substance has also been studied. Reduction of two a-keto acids to a-hydroxy acids has been effected in high yield, but only in the presence of Mg or Zn (as in enzymatic reactions of DPNH). Reduction involves direct transfer of hydrogen from the model compound. By use of a chiral derivative of 1-benzyl-1,4-di-hydronicotinamide reduction of ethyl benzoylformate to ethyl (R)-(-)-man-delate has been effected with an optical purity of 19%. 

Later, in 1979, Orito et al. studied novel catalysts containing noble metals (Pt-alumina and Pt-charcoal modified with cinchonidine) in the hydrogenation of MePy, MeBf, and EtBf Optical yields in the hydrogenation of ethyl benzoylformate, EtBf, to (R)-(-)-ethyl mandelate reached 89.5%... 

Niwa, S., Imai, S., Orito, Y. (1982) Asymmetric hydrogenation of ethyl benzoylformate using the platinum-carbon catalyst modified with cin-chonidine-influence of preparation of the catalyst on the asymmetric selectivity, J. Chem. Soc. Jpn. Nippon Kagaku Kaishi) Nl, 137-138. 

Figure The adsorption geometries for ethyl benzoylformate on the Pt(lll) surface. Carbon atoms are colored grey, hydrogen atoms white, oxygen atoms red and platinum atoms blue.

Another example of kinetic modehng requiring considerations of the number of adsorbed sites is enantioselective hydrogenation of ethyl benzoylformate (EBF) on a modified Pt/Al203 catalyst (Fig. 7.13). 

The kinetics of concerted thermal elimination reactions of a series of ethyl (hetero) arylcarboxylate esters (2-thienyl-, 3-thienyl-, 2-furyl, 3-furyl, 4-pyridyl-, 3-pyridyl-, and 2 -pyridylcarbo x y I ate) in the gas phase seem to indicate that there is tittle charge separation in the transition state (83) this is in contrast with the behaviour of the corresponding /-butyl and isopropyl esters for which a semi-concerted transition state (82) was proposed previously.49 Results of a kinetic study of the gas-phase elimination reactions of methylbenzoyl fonnate (84) and 3-hydroxy-3-methylbutan-2-one (85) have been compared with those for pyruvic acid (87) and benzoylformic acid (86).50 The relative rates of reaction [(86)/(87) 46, (87)/(85) = 1.1 x 105 and (86)/(82) = 1 x 106] reveal that the acidity of the hydrogen atom involved in the elimination process, rather than the initial polarization of the C—C bond which undergoes cleavage, is the important rate-controlling factor. 

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