Organic & Biomolecular Chemistry 2014-10-14

Nickel-catalyzed substitution reactions of propargyl halides with organotitanium reagents.

Qing-Han Li, Jung-Wei Liao, Yi-Ling Huang, Ruei-Tang Chiang, Han-Mou Gau

Index: Org. Biomol. Chem. 12(38) , 7634-42, (2014)

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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.