Chromium-catalyzed chemo- and regioselective synthesis of allenes from propargylic pivalates with Grignard reagents.

We report here an effective and practical pathway for the chromium-catalyzed chemo- and regioselective synthesis of allenes under ligand-free and mild conditions. This reaction utilized low-cost CrCl2 as the precatalyst, combined with easily available propargylic pivalates and Grignard reagents, a variety of allenes bearing a wide range of functional groups have been obtained with excellent yields in the absence of an external ligand.