Hydroxy alkenenitriles: diastereoselective conjugate addition-alkylations

Chelation-controlled conjugate addition of Grignard reagents to cyclic and acyclic gamma-hydroxyalkenenitriles stereoselectively generates beta-substituted hydroxynitriles. t-BuMgCl-induced deprotonation of gamma-hydroxyalkenenitriles followed by chloride-alkyl exchange from a second Grignard reagent, generates an alkylmagnesium alkoxide that triggers conjugate addition. Alkylation of the resulting magnesiated nitrile with alkyl halide and carbonyl electrophiles efficiently installs two new bonds and up to three stereocenters in a single synthetic operation.