Reversal of Diastereoselectivity in Reactions of the Trifluoroacetaldehyde Ethyl Hemiacetal with Enamines and Imines: Metal-Free, Complementary anti- and syn-Selective Synthesis of 4,4,4-Trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones

A complete reversal of diastereoselectivity was observed for reactions of the trifluoroacetaldehyde ethyl hemiacetal with enamines and imines, derived from propiophenones, that produce 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1 -butanones. This process serves as the first reliable, metal-free, complementary anti- and syn-selective method to prepare 4,4,4-trifluoro-1-aryl-3-hydroxy-2-methyl-1-butanones.