Reactions of Triplet Carbenes with Sulfides and Disulfides: Ylide vs. Radical Formation

Article abstract of DOI:10.1021/ja00271a035

The reactions between triplet diphenylcarbene and fluorenylidene with a variety of sulfides and disulfides were investigated with use of electron paramagnetic resonance (EPR) spectroscopy, laser flash photolysis, and product studies.Diphenylcarbene reacted with these substrates by a radical-like displacement mechanism.Rate constants were ca. 1E6 M_-1 s_-1, and the resulting thio-substituted diphenylmethyl radicals were identified by their EPR and optical spectra.By contrast, the analogous reactions of fluorenylidene had rate constants of 1E8-1E9 M_-1 s_-1 and proceeded by an ylide mechanism.Product studies were consistent with these results but were not sufficient in themselves to reveal these mechanistic differences.