Lewis acid mediated [3+2] and [3+3] annulations of azomethine imine with donor-acceptor cyclopropanes

The [3+2] and [3+3] regioselective cycloaddition reactions of azomethine imines with activated cyclopropanes have been developed using two different Lewis acids. Scandium (III) triflate serves as a catalyst for the [3+2] cycloaddition reactions of azomethine imines with cyclopropanes to form tetrahydropyrazolone derivatives and tricyclic tetrahydrofuran derivatives in moderate yields. In complementary to this, novel [3+3] cycloaddition reactions of azomethine imine with activated cyclopropanes have been developed using EtAlCl2 as a Lewis acid to form hexahydropyridazinone derivatives in high regioselectivity.