Baker's yeast mediated reduction of beta-keto esters and beta-keto amides in an organic solvent system

The baker's yeast mediated reduction of four beta -keto esters in petroleum ether indicated that the size of the group attached to the keto carbon aff ected their reactivity. Ethyl 3-phenyl-3-oxopropanoate (1), which has a phe nyl group directly attached to the keto carbon, is incompletely reduced usi ng 20 g yeast/mmol substrate, ethyl 4-phenyl-3-oxobutanoate (2), which has one methylene group between the phenyl and keto carbon, was also incomplete ly reduced using 20 g yeast/mmol, although the extent of reduction was abou t double that of (1), ethyl 5-phenyl-3-oxopentanoate (3), which has two met hylene groups between the phenyl and keto carbon, is completely reduced usi ng 10 g yeast/mmol and ethyl 3-oxobutanoate (4), which has a methyl group a ttached to the keto carbon shows complete reduction using only 1 g yeast/mm ol. The corresponding beta -keto amides are considerably less reactive than the corresponding beta -keto eaters with only the amides derived from ethy l 3-oxobutanoate indicating any significant reduction using 20 g yeast/mmol . (C) 2001 Elsevier Science B.V. All rights reserved.