Cyclization of oxa-bicyclic alkenes with beta-iodo-(Z)-propenoates and o-iodobenzoate catalyzed by nickel complexes: a simple efficient route to annulated coumarins.

In the presence of Ni(dppe)Br(2) and Zn powder in acetonitrile at 80 degrees C, oxa-bicyclic olefins undergo cyclization with o-iodobenzoate and with beta-iodo-(Z)-propenoates to give the benzocoumarin derivatives in moderate to good yields. This methodology offers a simple efficient way for the synthesis of structurally complicate coumarins in one pot. [reaction: see text]