Electron transfer induced dimerization of Spiro[4.2] heptadiene- -A facile radical cation diels alder reaction.

The electron transfer induced dimerization of spiro[4.2] heptadiene and the corresponding cleavage reaction of the [4+2]dimer have been investigated in polar solvents. CIDNP effects observed during these reactions are interpreted in terms of two different dimer radical cations a singly linked (S(.+)) and a doubly linked species (D.+)). These results require a nonconcerted (stepwise) cycloaddition and are the latest in a series of findings suggesting mechanistic variety for radical cation cycloadditions.