SYNTHESIS OF NEW 2H-1,4-THIAZINES AND THEIR DERIVATIVES UTILIZING N,N-(DI-N-ALKYL)-N'-ARYLTHIOCARBAMOYLAMIDINES

The reactions of N,N-(di-n-alkyl)-N'-arylthiocarbamoylamidines (1) wit h 2-bromo-1-phenylethanone in the presence of K2CO3 in THF at reflux g ave 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 i n the presence of pyridine in CH2Cl2 at 0 degrees C afforded 5-(di-n-a lkylamino)-6-arylimino-2H-1,4-thiazin-3- ones (12) in 41 to 84 % yield s, whereas the same reactions of 1 with 2-bromopropionyl bromide under the same conditions gave )-5-arylimino-2-(1-bromoethylidene)-2H-thiaz olines (17) as minor compounds in addition to thiazin-3-ones 16, analo gous to compounds 12. The reactions of 1 with ethyl bromoacetate in CH 2Cl2 at room temperature, however, gave )(S-ethoxycarbonylmethyl)]meth yl-N,N-(di-n-propyl) amide hydrobromides (19) in 71 to 88 % yields. Co mpounds 7, 12, 16, 17, and 19 are all new and the mechanisms of their formations are proposed. (C) 1998 Elsevier Science Ltd. All rights res erved.