Naphtho[1,2-b]thiophen. Part 2. Substitution reactions of derivatives with one or more substituents in the thiophen ring and of the 4,5-di-hydro-derivative

Abstract

Acetylation, formylation, and bromination of 2- or 3-methylnaphtho[1,2-b]thiophen and bromination of naphtho-[1,2-b]thiophen-3-carbaldehyde take place in the free thiophen position. Nitration of the 2-methyl compound gives mainly the 5-nitro-derivative and 2-methyl-2-nitronaphtho[1,2-b]thiophen-3(2H)-one; nitration of the 3-methyl compound gives a mixture of the 2- and 5-nitro-derivatives. 2,3-Dimethylnaphtho[1,2-b]thiophen undergoes bromination and acetylation in the 5-position. 4,5-Dihydronaphtho[1,2-b]thiophen undergoes mono-substitution in the 2-position; attempted nitration of its 2-ethoxycarbonyl derivative gave mainly the aromatised ethyl naphtho[1,2-b]thiophen-2-carboxylate and its 7-nitro-derivative.