Rhodium-catalyzed annulation reactions of 2-cyanophenylboronic acid with alkynes and strained alkenes.

[reaction: see text]. A new [3 + 2] annulation reaction was developed in which 2-cyanophenylboronic acid reacted as a three-carbon component with alkynes or alkenes to afford substituted indenones or indanones. The use of an alkynoate even produced benzotropone, a formal [3 + 2 + 2] adduct. The cyclic skeletons were constructed by intramolecular nucleophilic addition of an intermediate organorhodium(I) species to a cyano group.