Convenient Synthesis of α-Trifluoromethylated Acyloins from α-Hydroxy or α-Amino Acids

Abstract

α-Trifluoromethylated acyloins (2 and 6) have been prepared from α-hydroxy acids (1), N-acylprolines (5) or N-acyl-N-alkyl α-amino acids (8) by novel transformation reactions with trifluoroacetic anhydride (TFAA) in the presence of pyridine. The former reaction of 1 could proceed through mesoionic 1, 3-dioxolium-4-olates, whereas the latter two reactions of α-amino acids (5 and 8) could involve mesoionic 1, 3-oxazolium-5-olates. The reaction of 1 with TFAA shows more potential for practical applications because of the ready availability of the starting materials and ease of manipulation.