Rhodium(III) Porphyrin-catalyzed Reactions via Activation of Alkynes

The cycloisomerization of 1,6-enynes catalyzed by rhodium(III) porphyrin under mild reaction conditions successfully afforded a five-membered ring system. The rhodium porphyrin was found to be a strong it-Lewis acid that could activate alkynes. Thus, rhodium porphyrin-catalyzed intramolecular Friedel-Crafts-type reactions of alkynes with arenes were also accomplished. Furthermore, rhodium porphyrin-catalyzed intermolecular cyclization of alkynes with styrenes afforded the indene derivatives.