Synthesis of Pyrimido[2,1-b]benzoxazolium, Pyrimido[2,1-b]benzothiazolium and Pyrimido[1,2-a]benzimidazolium Salts by Reaction of 3-Isothiocyanato-2-propeniminium Salts witho-Functionalized Anilines
摘要:
3-Isothiocyanato-2-propeniminium salts 1 react with o-phenylenediamine, o-aminophenol or o-aminothiophenol to give o-substituted 1-phenyl-2(1H)-pyrimidinethiones 4, which cyclize upon treatment with methyl iodide to afford pyrimido[2,1-b]benzoxazolium, pyrimido[2,1-b]benzothiazolium and pyrimido[1,2-a]benzimidazolium salts 5 (X = O, S or NH, respectively) by a new condensation reaction.