Exploitation of donor-acceptor cyclopropanes and N-sulfonyl 1-azadienes towards the synthesis of spiro-cyclopentane benzofuran derivatives.

A MgI catalyzed formal [3 + 2] cycloaddition reaction between donor-acceptor cyclopropanes and N-sulfonyl 1-azadienes towards the synthesis of highly functionalized spiro-cyclopentane benzofuran derivatives has been developed. This methodology is appreciated in terms of chemoselectivity and mild reaction conditions. In addition, hydrolysis of one of the N-sulfonyl derivatives offered the corresponding spiro dihydrofuran-3-one derivative in the presence of basic alumina.