Highly Efficient Intra- and Intermolecular [4 + 2] Cycloaddition Reaction Catalyzed by Rhodium Complex

A cationic Rh(Ι) complex, [(η 6 -C 10 H 8 )Rh(cod)]BF 4, has been found to be a quite useful catalytic system for both the intermolecular [4 + 2] cycloaddition reaction of 1,3-dienes with nonactivated acetylenes and the intramolecular [4 + 2] cycloaddition of dienyne under very mild reaction conditions (CH 2 Cl 2, 15 °C, 15 min).