ELECTRON-TRANSFER PHOTOCHEMISTRY OF CHRYSANTHEMOL - AN INTRAMOLECULARS(N)2' REACTION OF A VINYLCYCLOPROPANE RADICAL-CATION

The electron transfer photochemistry of optically pure (1R,3S)-(f)-cis -chrysanthemol (cis-2) results in the formation of R)-5-(1-(p-cyanophe nyl)-1-methyethyl)-2,2-dimethyl oxacyclohex-3-ene (4) with significant retention of optical activity. The product is rationalized via nucleo philic attack of the alcoholic function of the radical cation on the t erminal carbon of the vinyl group with simultaneous replacement of an isopropyl radical as an intramolecular leaving group in an apparent S( N)2' reaction. This mode of attack is unprecedented in vinylcyclopropa ne radical cations and is interpreted as evidence for the significant role that relief of ring strain and its avoidance play in determining the course of nucleophilic capture in radical cationic systems.