Cyclization Reaction of Cyano-Substituted Unsaturated Esters Prompted by Conjugate Addition of Organoborons

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 β-enamino esters in good yield. An (oxa-π-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.