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。