Partially fluorinated heterocyclic compounds. Part IV. The preparation of 4,5,6,7-tetrafluoroindole by a new cyclisation reaction

Abstract

Treatment of the sodium salt of pentafluoroaniline with diethyl acetylenedicarboxylate in tetrahydrofuran gave a stable secondary vinylamine, diethyl N-(2,3,4,5,6-pentafluorophenyl)aminofumarate which with sodium hydride in NN-dimethylformamide gave 2,3-diethoxycarbonyl-4,5,6,7-tetrafluoroindole. Hydrolysis of this indole and decarboxylation of the 2-carboxylic acid gave 4,5,6,7-tetrafluoroindole which formed a 1 : 1 molecular addition complex with quinoline.