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Three at a time: Sequential carbonyl addition, chelation‐controlled conjugate addition, and alkylation triggers the multicomponent assembly of diverse nitriles. The chelation‐controlled conjugate addition–alkylation installs three new stereocenters (see scheme), thereby generating substituted nitriles that are ideal terpenoid precursors as illustrated in the synthesis of epi‐dehydroabietic acid.

Temporarily anchoring Grignard and organolithium reagents to gamma-hydroxy-alpha,beta-alkenenitriles promotes efficient conjugate additions to what are otherwise recalcitrant Michael acceptors. Sequential deprotonation and addition of a modest excess of a second Grignard reagent allows effective conjugate delivery of alkyl groups to cyclic and acyclic alkenenitriles. Mechanistically, conjugate additions proceed through alkylmagnesium alkoxide complexes for all but the more substituted alkenenitriles that require alkyl transfers from the more reactive ate complexes. Synthetically, chelation-controlled conjugate additions rapidly, and stereoselectively, assemble substituted nitriles, installing up to two new stereocenters in a single synthetic operation.

[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.