[4+2] Cycloaddition Reactions between 2,4-Diamino-1-thia-3-azabutadienes and Ketene. Synthesis of New 1,3-Thiazin-6-ones, 1,3-Thiazine-6-thiones and 2-Thioxopyrimidin-4-ones

Abstract

The reaction of 2,4-diamino-1-thia-3-azabutadienes with an excess of ketene afforded 2-amino-1,3-thiazin-6-ones and 2-thioxopyrimidin-4-ones by [4+2] cycloaddition reaction.Reaction between thiazabutadienes and ketene gave rise to aminothiazinones, which were sulfured by action of phosphorus pentasulfide leading to aminothiazinethiones. Furthermore, synthesis of thioxopyrimidinones starting from S-methyl salts of thiazadienes is described.