Unsaturated Nitriles: Stereoselective MgO Eliminations.

α,β-Unsaturated nitriles are readily synthesized by eliminating MgO from β-hydroxynitriles. Deprotonating acyclic, and cyclic, β-hydroxynitriles with excess MeMgCl smoothly generates dianion intermediates that eject MgO with concurrent formation of α,β-unsaturated nitriles. Alternatively, sequential addition of lithioacetonitrile and MgBr2 to aldehydes and ketones generates magnesium alkoxides in situ that eliminate MgO upon addition of MeMgCl. The MeMgCl-induced MgO eliminations smoothly generate α,β-unsaturated nitriles from hindered ketones that are otherwise difficult to synthesize.