gamma-hydroxy unsaturated nitriles: chelation-controlled conjugate additions.

[reaction--see text] Chelation between gamma-hydroxy unsaturated nitriles and Grignard reagents promotes an otherwise difficult anionic conjugate addition reaction. The intermediate chelate is readily generated by deprotonation with t-BuMgCl followed by the addition of a second Grignard reagent that triggers an intramolecular conjugate addition. Structurally diverse Grignard reagents add with equal efficiency, providing an intermediate anion that stereoselectively alkylates BnBr in an overall addition-alkylation reaction.