Cyclization reaction of cyano-substituted unsaturated esters prompted by conjugate addition of organoborons.

[reaction: see text] Unsaturated esters possessing a pendent cyano moiety react with B-Ar-9-BBNs in the presence of a rhodium(I) catalyst to give the five- and six-membered beta-enamino esters in good yield. An (oxa-pi-allyl)rhodium(I) intermediate, formed by initial conjugate addition of an Ar-rhodium(I) species, undergoes a facile intramolecular addition to the cyano group to construct the carbocyclic skeletons.