Asymmetric synthesis of trifluoromethylated propargylamines via 1,2-additions of trifluoromethylacetylide to N-tert-butanesulfinyl imines

An efficient method for the asymmetric synthesis of the trifluoromethylated propargylamines was described. Addition of lithium trifluoromethylacetylide, in situ prepared from lithium diisopropylamide and the 2-bromo-3,3,3-trifluoropropene, to various N-tert-butanesulfinyl imines provided a range of trifluoromethylated propargyl sulfinamides. Besides high yields and excellent diastereoselectivities, the additions featured that the diastereoselectivities could be reversed when polar or nonpolar solvent was used. Acidic cleavage of the tert-butanesulfinyl groups delivered highly optically pure trifluoromethylated propargylamines.