Lewis Acid Triggered Vinylcyclopropane-Cyclopentene Rearrangement

We report a mild Lewis acid induced isomerization of donor acceptor cyclopropanes, containing an alkenyl moiety and diverse electron -withdrawing group(s) at the adjacent positions, into substituted cyclopentenes. We have found that 1,1,2-trisubstituted cydopent-3-enes were exclusively obtained in yield of 51-99% when cyclopropanes with a 2 -substituted alkenyl group as a donor underwent isomerization. For cyclopropanes bearing a trisubstituted alkenyl group either the corresponding cydopent-3-enes or isomeric cydopent-2-enes having two acceptor groups at the C(1) atom formed, with the reaction selectivity being determined by the applied Lewis acid. We have shown that the reactivity of the donor acceptor cyclopropane increases with the increase of the electron -donating character of (hetero)aromatic group attached to the alkenyl moiety. The synthetic utility of the developed methodology was also demonstrated through the synthesis of polysubstituted cyclopentane and piperidine derivatives.