Cyclization of N-alkyl azinium cations with bifunctional nucleophiles. 21. Regioisomeric 1,3,4-thiadiazino[5,6-b]quinoxalines

Thiobenzhydrazides undergo cyclization with N-alkyl-quinoxalinium salts to give 5-alkyl-substituted 1,4,4a,5,10,10a-hexahydro-1,3,4-thiadiazino5,6-b]quinoxalines, which undergo isomerization to 10-alkyl-substituted thiadiazinoquinoxalines when they are heated in ethanol or in the presence of acids.See 1] for Communication 20.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 557–561, April, 1987.