Abstract: The synthesis of dihydropyrimidines, dihydropyrimidinones and thiadiazine-1, 1- dioxides starting from neutral or cationic 2-methylthio-1, 3-diazadienes is described. Addition of H2S followed by loss of methanethiol led to the corresponding thiocarbonyl compounds. Key words: 1, 3-diazadienes,[4+ 2] cycloaddition, dihydropyrimidines, dihydropyrimidinones, thiadiazinedioxides
