2-Trifluoromethyl-2-methyl-4-phenyloxazolidine: A new chiral auxiliary for highly diastereoselective enolate alkylation

The alkylation reactions of an amide sodium enolate derived from a C-2 disubstituted trifluoromethylated oxazolidine (Fox) chiral auxiliary occurred in good yields with a very high diastereoselectivity (>98% de). Compared to the C-2 monosubstituted trifluoromethyl analogue, this chiral auxiliary is much more stable towards bases at temperature over −35 °C because the dehydrofluorination reaction is avoided. However asymmetric enolates quaternarization was not successfully achieved with this new chiral auxiliary.