Unsaturated nitriles: stereoselective MgO eliminations

Alpha,beta-unsaturated nitriles are readily synthesized by eliminating MgO from beta-hydroxynitriles. Deprotonating acyclic, and cyclic, beta-hydroxynitriles with excess MeMgCl smoothly generates dianion intermediates that eject MgO with concurrent formation of alpha,beta-unsaturated nitriles. Alternatively, sequential addition of lithioacetonitrile and MgBr(2) to aldehydes and ketones generates magnesium alkoxides in situ that eliminate MgO upon addition of MeMgCl. The MeMgCl-induced MgO eliminations smoothly generate alpha,beta-unsaturated nitriles from hindered ketones that are otherwise difficult to synthesize.