Asymmetric Reformatsky Reaction with a Chiral Oxazolidinone Auxiliary

Significance

This is the first enantioselective synthesis of α-trifluoromethyl-β-hydroxycarboxylic acid derivatives via highly syn-selective Evans aldol and highly anti-selective Reformatsky reactions. Aromatic aldehydes afford the best yields and stereoselectivity. The use of 0.1 equivalent of TiCl₄ caused a significant decrease of the yield (from 71% to 27%). The silyl ketene acetal was used without purification. A reaction mechanism is proposed to explain and predict the stereochemical outcome.