Regioselective addition reactions of group IVb organometallic radicals with p-diones. An ESR study

The Group IVB organometallic adducts of a number of substituted p-diones and related compounds have been investigated by ESR spectroscopy. In the case of substrates with unequivalent carbonyl groups two distinct isomeric adducts have been detected, and the factors affecting the regioselectivity of the addition reaction are discussed. The magnitude of the hyperfine splitting constants at the metal atoms and the trend of the g-values are consistent with a conformation for the adducts where the organometallic substituent eclipses the p orbital of the radical c entre.