Competitive Reaction Pathways for o-Anilide Aryl Radicals: 1,5- or 1,6-Hydrogen Transfer versus Nucleophilic Coupling Reactions. A Novel Rearrangement to Afford an Amidyl Radical

REY, V.; PIERINI, A. B.; PEÑÉÑORY, A. B.

American Chemical Society

Año: 2009 vol. 74 p. 1223 - 1223

he photoinduced reactions of o-iodoanilides (o-IC6H4N(Me)COR, 4a-d) with sulfur nucleophiles such as thiourea anion (1, -SCNH(NH2)), thioacetate anion (2, MeCOS-) and sulfide anion (3, S2-) follow different reaction channels, giving the sulfides by a radical nucleophilic substitution or the dehalogenated products by hydrogen atom transfer pathways. After an initial photoinduced electron transfer (PET) from 1 to iodide 4, the o-amide aryl radicals 12 are generated. These aryl radicals 12 afford alternative reaction pathways depending on the structure of the -carbonyl moiety: a) 12b (R = Me) adds to 1 to render the methylthio-substituted compounds by quenching the thiolate anion intermediate with MeI after irradiation; b) 12c (R = -CH2Ph) follows a 1,5-hydrogen transfer to give a stabilized -carbonyl radical (17); and c) 12d (R = t-Bu) affords 1,6-hydrogen transfer, followed by a 1,4-aryl migration to render an amidyl radical (20), which is reduced to the N-benzyl-N,2-