OXIDATION OF 2-(4-CHLOROBENZOYL)-THIOPHENE INTO 1-OXIDE DIELS-ALDER DIMERS, SESQUIOXIDE AND A SULFONE-WATER ADDUCT

Oxidation of 4-chlorophenyl, thien-2-yl-methanone 1 with 0.2 eq H2O2 i n TFA gave the 1-oxide Diels-Alder dimer 3a. Use of an 1-5 eq H2O2 aff orded the sesquioxide 4 (4,7 di [4-chlorobenzoyl]-3,10-dithiatricyclo [5.2.1.0(2,6)] deca-4,8-diene 3,3,10-trioxide). Oxidation of 1 with mC PBA in CH2Cl2-excess BF3-etherate gave 3a (4,7-di [4-chlorobenzoyl]-3, 10-dithiatricyclo [5.2.1.0(2,6)] deca-4,8-diene 3,10-dioxide) in accep table yield and the minor isomer 3b in low yield. Oxidation of 1 with 6 eq dimethyldioxirane in acetone gave 3-hydroxy 2,3-dihydrothiophene 1,1-dioxide 6, a 1,1-dioxide-water adduct. (C) 1998 Elsevier Science L td. All rights reserved.