Syntheses of new mesoionrc compounds

Abstract

New mesoionic compounds were synthesized from the reaction of chlorosulfonly isocynate (CSI) or pentachlorophenyl N-chlorosulfonylcarbamate (PCPCSC) with amidine compounds in the presence of ethyldiisopropylamine. CSI or PCPCSC reacted with 2-benzylaminopyridine producing intermediate which was cyclized to afford mesoionic 1-benzylpyrido[1,2-b][1,2,4,6]thiatriazine-2,4,4-trioxide in the presence of tertiary amine base at room temperature. 2-Alkylaminothiazoles afforded mesoionic 1-alkylthiazolo[2,3-c][1,2,4,6]thiatriazine-2,4,4-trioxides with CSI and mesoionic 1-alkylthiazolo[3,2-b]-[1,2,4,6]thiatriazine-2,4,4-trioxideswith PCPCSC in the presence of a tertiary amine base in chloroform at room temperature, respectively. 2-Alkylaminobenzothiazoles frequently gave mixture of mesoionic 4-alkylbenzothiazolo[2,3-c][1,2,4,6]thiatriazine-1,3,3-trioxides and 4-alkylbenzothiazolo-[3,2-b][1,2,4,6]thiatriazine-1,1,3-trioxides with CSI or PCPCSC in the presence of a tertiary amine base. Monocyclic mesoionic compounds were also synthesized. Mesoionic [1,2,4,6]thiatriazine-1,1,3-trioxides were obtained from the reaction of N,N``-disubstituted amidines with CSI or PCPCSC in the presence of ethyldiisopropylamine in chloroform at room temperature. CSI and PCPCSC were good reagents for the synthesis of mesoionic compounds with 1,3-dinitrogen nucleophiles in the presence of ethyldiisopropylamine under mild conditions.