Nickel-catalyzed substitution reactions of propargyl halides with organotitanium reagents

Abstract

A simple and mild catalytic coupling reaction of propargyl halides with organotitanium reagents is reported. The reaction of propargyl bromide with organo-titanium reagents mediated by NiCl₂ (2 mol%) and PCy₃ (4 mol%) in CH₂Cl₂ afforded coupling product allenes in good to excellent yields (up to 95%) at room temperature. However, NiCl₂(PPh₃)₂ was the best catalyst for substituted propargyl halides to yield allenes or alkynes preferentially. On the basis of the experimental results, a possible catalytic cycle has been proposed.