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

A protocol\nfor the construction of cycloheptatrienes has been developed.\n4-(Dimethylamino)pyridine (DMAP) was found to be an efficient catalyst\nto promote the [4 + 3] annulation between coumalates and γ-alkyl-substituted\nallenoate or γ-aryl-3-butynoates to deliver a variety of cycloheptatrienes\nin moderate to good yield with excellent chemoselectivity. The asymmetric\nversion of this annulation was also realized by using bifunctional\nphosphine catalyst to provide the chiral products with 32–97%\nee and 29–64% yield.