Rapid Construction of Cycloheptatriene through Organocatalyzed [4 + 3] Annulation of Coumalates.

A protocol for the construction of cycloheptatrienes has been developed. 4-(Dimethylamino)pyridine (DMAP) was found to be an efficient catalyst to promote the [4 + 3] annulation between coumalates and γ-alkyl-substituted allenoate or γ-aryl-3-butynoates to deliver a variety of cycloheptatrienes in moderate to good yield with excellent chemoselectivity. The asymmetric version of this annulation was also realized by using bifunctional phosphine catalyst to provide the chiral products with 32-97% ee and 29-64% yield.