Facile synthesis of α-difluoromethyl α-propargylamines from CF2H-substituted N-tert-butanesulfinyl ketimines

Stereoselective approach for preparation of α-difluoromethyl α-propargylamines has been developed. 1,2-Addition of lithium acetylides to diverse chiral difluoromethylated (S)-N-tert-butanesulfinyl ketimines by using Ti(OiPr)4 as catalyst and THF as solvent afforded N-tert-butanesulfinamides in good to excellent yields (51–93%) and good diastereoselectivities (dr. 85:15 to 93:7). The N-tert-butanesulfinyl group can be readily cleaved under mild acidic condition (4 mol/L HCl in dioxane) to provide the corresponding α-difluoromethyl α-propargylamine in excellent yields (90–95%).