Reactions of o-Iodohalobenzenes with Carbanions of Aromatic Ketones. Synthesis of 1-Aryl-2(o-halophenyl)ethanones

BAUMGARTNER, M. T; JIMENEZ, LILIANA B.; PIERINI, A.B.; ROSSI, R.A.

Chemical Society

Lugar: London; Año: 2002 p. 1092 - 1092

-Iodohalobenzenes (X = I, Br, Cl) react in DMSO with the enolate ions of acetophenone, propiophenone and 1-(2-naphthyl)ethanone to afford mainly monosubstitution with retention of one halogen. The monosubstituted dehalogenated compounds are formed in low overall yields in the reactions of o-diiodobenzene with the carbanions of 1-(2-naphthyl)ethanone and of acetophenone and in the reaction of o-bromoiodobenzene with the carbanion of propiophenone. The reactions can be performed in the dark, with usually increased yields of substitution under irradiation, as well as under FeBr2 initiation. Treatment of 2-(2-bromophenyl)-1-phenylethanone with Cu bronze affords the ring closure benzofuran product. The degree of dehalogenation is discussed in terms of the energetics of the intramolecular electron transfer (ET) from the ArCO-π system to the C–halogen σ bond in the monosubstituted radical anions proposed as intermediates. The lack of ring closure of the radicals formed by dehalogen