Radical adducts of dibenzofulvenes and 9-methylenanthrone - an esr study

The title compounds were reacted with a series of R3M. radicals (M = C, Si, Ge, Sn; P, O, S) to give the corresponding paramagnetic adducts. In the case of 9-methylenanthrone radical addition occurred selectively at the hexocycli carbon-carbon double bond even with group IVB organometallic radicals for which attack at the carbonyl oxygen would give rise to thermodynamically more stable adducts. When irradiating solutions of 9-methylenanthrone a photoinduced self-reaction leading to the formation of dimeric species took place. On the basis of the measured ESR spectral parameters the structure of the adducts is discussed, as well as the influence of the RnM groups on the beta-proton hyperfine splitting constants.