S-alkylation of pyridinium 1-(thiocarbonyl)methylides with various alkyl bromides such as bromoacetonitrile, ethyl bromoacetate, and some phenacyl bromides, gave smoothly 1,9a-dihydropyrido[2,1-c][1,4]thiazine derivatives as almost isomeric mixtures. These dihydropyridothiazines are very unstable and decomposed rapidly at ordinary temperature, but by treating them with a dehydrogenating agent such
1-[2-(取代甲硫基)乙烯基]吡啶鎓溴化物的碱处理,很容易从吡啶鎓1-(硫代羰基)甲基化物与各种烷基溴化物如溴乙腈、溴乙酸乙酯和一些苯甲酰溴化物的S-烷基化获得,顺利地得到1,9a-二氢吡啶并[2,1-c][1,4]噻嗪衍生物几乎是异构体混合物。这些二氢吡啶并噻嗪非常不稳定,在常温下分解迅速,但在 0 °C 下用四乙酸铅 (LTA) 或 2,3-二氯-5,6-二氰基-对苯醌 (DDQ) 等脱氢剂处理它们以中等至良好的产率形成脱硫和重排的芳族茚茚衍生物。