Convenient Asymmetric Synthesis of β-Trifluoromethyl-β-amino Acid, β-Amino Ketones, and γ-Amino Alcohols via Reformatsky and Mannich-Type Reactions from 2-Trifluoromethyl-1,3-oxazolidines

The stereoselective syntheses of beta-trifluoromethyl-beta-amino ester, beta lactams, and beta-amino ketones starting from an oxazolidine derived from trifluoroacetaldehyde hemiacetal and (R)-phenylglycinol are reported. The Mannich-type reaction involving a chiral fluorinated iminium ion occurred in a good yield and with a higher stereoselectivity (dr up to 96:4) than that of the Reformatsky-type reaction. This straightforward strategy was applied to the short syntheses of (R)-3-amino-4,4,4-trifluorobutanoic acid, a series of novel enantiopure unprotected fluorinated beta-amino ketones, and their corresponding gamma-amino alcohols.