Lewis Acid Mediated [3+2] and [3+3] Annulations of an Azomethine Imine with Donor-Acceptor Cyclopropanes

Two different Lewis acids were used for developing [3+2] and [3+3] regioselective cycloaddition reactions of an azomethine imine with activated cyclopropanes. Scandium(III) triflate catalyzes a [3+2] cycloaddition reaction of the azomethine imine with cyclopropanes to form tetrahydropyrazolone derivatives and tricyclic tetrahydrofuran derivatives in moderate yields. Complementary to this, a novel [3+3] cycloaddition reaction of the azomethine imine with activated cyclopropanes was developed by using EtAlCl2 as a Lewis acid to form hexahydropyridazinone derivatives in high regioselectivity.

Automated summary

Two different Lewis acids were utilized to achieve regioselective [3+2] and [3+3] cycloaddition reactions of an azomethine imine with activated cyclopropanes, resulting in moderate yields of tetrahydropyrazolone derivatives and tricyclic tetrahydrofuran derivatives as well as high regioselectivity in forming hexahydropyridazinone derivatives.