Reactions of o-iodohalobenzenes with carbanions of aromatic ketones. Synthesis of 1-aryl-2-(o-halophenyl)ethanones.

LILIANA B. JIMENEZ

JOURNAL OF THE CHEMICAL SOCIETY. PERKIN TRANSACTIONS 2 (2001)

Royal Society of Chemistry

Año: 2002 p. 1092 - 1092

1472-779X

-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 compds. 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 irradn., 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 intramol. electron transfer (ET) from the ArCO-.pi. system to the C-halogen .sigma. bond in the monosubstituted radical anions proposed as intermediates.  The lack of ring closure of the radicals formed by dehalogenation o