A Cascade Annulation of Enals and Dienones

Significance

The authors describe a highly ­regio- and stereoselective cascade annulation of enals 1 and benzodi(enone)s 2 catalyzed by chiral NHCs. By controlling the electronic properties of the dienones, regioselective annulations of unsymmetrical dienones could also be achieved. The previously reported cyclopentene derivatives 5 were not detected (see also: V. Nair et al. J. Am. Chem. Soc. 2006, 128, 8736).