Synthesis of new 2H-1,4-thiazines and their derivatives utilizing N,N-(di-n-alkyl)-N'-arylthiocarbamoylamidines

Article abstract of DOI:10.1016/S0040-4020(98)00010-6

The reactions of N,N-(di-n-alkyl)-N'-arylthiocarbamoylamidines (1) with 2-bromo-l-phenylethanone in the presence of K₂C0₃ in THF at reflux gave 3-(di-n-alkylamino)-2-arylimino-5-phenyl-2H-1,4-thiazines (7) in 32 to 62% yields. Treatment of compounds 1 with bromoacetyl bromide in the presence of pyridine in CH₂Cl₂ at 0°C afforded 5-(di-n-alkylamino)-6-arylimino-2H-1,4-thiazin-3-ones (12) in 41 to 84% yields, whereas the same reactions of 1 with 2-bromopropionyl bromide under the same conditions gave 4-(di-n-alkylamino)-5-arylimino-2-(1-bromoethylidene)-2H-thiazolines (17) as minor compounds in addition to thiazin-3-ones 16, analogous to compounds 12. The reactions of 1 with ethyl bromoacetate in CH₂Cl₂ at room temperature, however, gave [(arylimino)(S-ethoxycarbonylmethyl)]methyl-N,N-(di-n-propyl)amidine hydrobromides (19) in 71 to 88% yields. Compounds 7, 12, 16, 17, and 19 are all new and the mechanisms of their formations are proposed.