Substitution reactions of benzo[b]thiophen derivatives. Part II. Nitration and bromination of 2-bromo-3-methylbenzo[b]thiophen

Abstract

Nitration of 2-bromo-3-methylbenzo[b]thiophen under three different sets of conditions gave in each case a mixture of the 4-(14–18%) and 6-nitro-compounds (21–27·5%) and 3-methyl-3-nitrobenzo[b]thiophen-2(3H)-one (35–47%). Structures were established spectroscopically; those of 2-bromo-3-methyl-4-nitrobenzo[b]thiophen and 3-methyl-3-nitrobenzo[b]thiophen-2(3H)-one were confirmed by synthesis. Attempted distillation of the latter gave 3-hydroxy-3-methylbenzo[b]thiophen-2(3H)-one, which could also be obtained by treatment of benzo[b]thiophen-2,3-dione with methylmagnesium iodide.

Bromination of 2-bromo-3-methylbenzo[b]thiophen gave a single product, which was probably the 6-bromoisomer.