The Cyclopropyl Group as a Neglected Donor in Donor-Acceptor Cyclopropane Chemistry.

D-A cyclopropanes bearing a simple cyclopropyl group as donor are shown to undergo a variety of [3+ n]-cycloaddition reactions ( n = 2-4). This behavior contrasts sharply with that of common D-A cyclopropanes with aliphatic donors. Kinetic experiments demonstrate that, in terms of donor ability, the cyclopropyl substituent lies between electron-rich and electron-neutral aryl donors.