Intramolecular 6-endo-dig-Cyclization of Ethyl 5-Aminomethyl-4-(1,2,3-thiadiazol-4-yl)furan-2-carboxylate

Abstract

The reaction of 5-aminomethyl-4-(1,2,3-thiadiazol-4-yl)furan-2-carboxylic acid ethyl ester with bases has given ethyl 5-sulfanylidene-4,5,6,7-tetrahydrofuro[2,3-c]pyridine-2-carboxylate as a result of intramolecular 6-endo-dig-cyclization of thioketene generated in situ with an internal CH₂NH₂ nucleophile. The obtained ester has been alkylated with iodomethane at the sulfur atom to form ethyl 5-methylsulfanyl-4,7-dihydrofuro[2,3-c] pyridine-2-carboxylate. The Hantzsch reaction with ω-bromoacetophenone has resulted in the formation of 7-ethoxycarbonyl-3-phenylfuro[3,2-d[1,3]thiazolo[3,2-a]pyridin-4-ium bromide.