Xanthenyl radicals

Xanthenyl radicals have been implicated in the oxidation of xanthene in various conditions. Contrasting mechanisms have been advanced for the acid-catalyzed autoxidation of xanthene. The result of oxidation of xanthene by superoxide ion in DMSO is consistent with the intermediacy of 38 it may also have a role in oxidation by ceric ammonium nitrate. 2.i83... 

The exclusive addition of the xanthene moiety to the sterically less hindered carbonyl group was observed in 15b, in accordance with the lower reactivity of dimethyl-substituted 15c. The CIDNP experiment revealed that 16 and 17 are recombination products via an initially formed triplet radical pair. The proposed mechanism is shown in Scheme 11. The hydrogen abstraction of the excited triplet state of 15 from xanthene generates ketyl and xanthenyl radicals. A possible product derived from outer cyclopropane bond cleavage was not obtained because of the lower stability of a primary radical compared with the conjugated radical formed by inner cyclopropane bond cleavage. 

Free electron transfer from xanthenyl and fluorenylsilanes (Me-3 or Ph-3) to parent solvent radical cations Effect of molecule dynamics. J Phys Chem A 109 11679-11686. 

When xanthene is oxidized by certain 1,4-naphthoquinones, radical products are obtained which contain a xanthenyl moiety (e.g., 42) for which splittings are quoted in gauss. The reactions have been investigated by the CIDNP technique. Radical 41 has been involved as a substrate in Feldman and co-workers series of papers on stabilities of trivalent carbon spe-144.185,186 Section II,B,5,e for radicals from xanthene dyes.)... 

Radical Rearrangement. The Mn(OAc)3-promoted oxidation of monoalkyl 2-(9//-xanthenyl)malonates gives the 9- or 10-dibenz[fc/ oxepincarhoxylates in good yields (eq 37). In most cases, regioselectivity is excellent. ... 

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