Electron transfer photochemistry of 7-(spirocyclopropane)quadricyclane: capture of a radical cation and sequential cyclopropylcarbinyl rearrangements

Abstract

The electron transfer photo-sensitized reaction of 7-(spirocyclopropane)quadricyclane (1) with methanol produces two rearranged mono-methanol adducts, 2 and 3, and a bis-methanol adduct, 4. The products reveal that 1·+ reacts by stereo- and regiospecific attack of methanol on one trisubstituted cyclopropane ring. The resulting free radical rapidly undergoes one or two (consecutive) cyclopropylcarbinyl to butenyl rearrangements. The mono-adducts are formed by net hydrogen abstraction, the di-adduct via a (secondary) electron transfer reaction of 3. © 1997 John Wiley & Sons, Ltd.