SYNTHESIS OF L)-(1-OXO-1-LAMBDA(4)-BENZO[B]THIEN-2-YL)METHANONE AND STUDY OF ITS REACTIVITY TOWARDS SULFUR-CONTAINING AND OXYGEN-CONTAININGNUCLEOPHILES

(4-Chlorophenyl)-(1-oxo-1 lambda(4)-benzo[b]thien-2-yl)methanone 2a wa s synthesized by oxidation of the corresponding benzo[b]thiophene deri vative 2 with the oxidative system H2O2/TFA. This benzo[b]thiophene su lfoxide undergoes Michael-type nucleophilic addition of sulfur- and ox ygen-containing nucleophiles either under basic conditions leading to 2,3-dihydro-3-substituted-benzo[b]thiophene 1-oxides or in acidic medi a leading then to rearomatized 3-substituted-benzo[b]thiophenes. This method provides an easy two-step functionalization of 2-acyl-benzo[b]t hiophene derivatives. (C) 1998 Elsevier Science Ltd. All rights reserv ed.