Aromatic polyfluoro-compounds. Part XL. The preparation and some nucleophilic replacement reactions of 4,5,6,7-tetrafluorobenzo(b)-thiophen

Abstract

Reaction of pentaflurorobenzaldehyde with rhodanine gave 2,3,4,5,6-pentafluorobenzylidenerhodanine; thence, by basic hydrolysis and a new intramolecular cyclisation, 4,5,6,7-tetrafluorobenzo[b]thiophen-2-carboxylic acid was prepared. Decarboxylation then afforded 4,5,6,7-tetrafluorobenzo[b]thiophen. 4,5,7-, 4,6,7-, and 5,6,7-Trifluorobenzo[b]thiophen were made by similar series of reactions from tetrafluorobenzaldehydes. Some nucleophilic replacement reactions with sodium methoxide, potassium hydroxide, and hydrazine hydrate at position 6 of the 4,5,6,7-tetrafluorobenzo[b]thiophen are described.