Catalytic Asymmetric Addition of Alkyl and Aryl Alkynes to N-(Diphenylphosphinoyl)imines

A 3,3'-di(1-diphenylmethylpiperazinyl)methyl. H8BINOL compound, (S)-11, was prepared from the Mannich-type reaction of (S)-H8BINOL with paraforrnaldehyde and 1-(diphenylmethyl)piperazine. This compound can catalyze the asymmetric reaction of alkyl and aryl alkynes with N-(diphenylphosphinoyl)imines in the presence of Et2Zn and Ti((OPr)-Pr-i)(4). It exhibits unprecedented high enantioselectivity (up to 85% ee) for a simple alkyl alkyne addition to the N-(diphenylphosphinoyl)imines. The easy removal of the N-(dipehenylphosphinoyl) protecting groups makes this method practically useful for the asymmetric synthesis of chiral propargyl amines.