Some reactions of 7-hydroxy- and 7-mercapto-3-methylbenzo[b]thio-phen

Abstract

Bromination of 7-hydroxy-3-methylbenzo[b]thiophen gave the 4- and the 6-monobromo- and the 4, 6-dibromo-derivative. Nitration gave the 6-nitro- and the 4,6-dinitro-derivative, and formylation by the Gattermann reaction gave the 6-formyl derivative. 7-Allyloxy-3-methylbenzo[b]thiophen underwent the Claisen rearrangement to give the expected 6-allyl compound, whereas Fries rearrangement of the 7-acetoxy-compound gave 2-acetyl-7-hydroxy-3-methylbenzo[b]thiophen. With ethyl acetoacetate in the presence of gaseous hydrogen chloride, 7-hydroxy-3-methylbenzo[b]thiophen condensed to give 3,6-dimethylthieno[3,2-h][1]benzopyran-8-one, 7-Mercapto-3-methylbenzo[b]thiophen and 2-bromopropionic acid in alkaline solution gave 2-(3-methyl-7-benzo[b]thienylthio)propionic acid, which was cyclised in hot polyphosphoric acid to give 7.8-dihydro-3-methyl-thieno[3,2-h][1]benzothiopyran-6-one.