Nickel-catalyzed [4+3] cycloaddition of ethyl cyclopropylideneacetate and 1,3-dienes

The [4+3] cycloaddition of ethyl cyclopropylideneacetate (1) with 1,3-dienes proceeded in the presence of Ni(cod)2–TOPP (tri-o-biphenylyl phosphite). The reaction provided a new method for the synthesis of cycloheptene derivatives. The mechanism of the reaction was proposed.