以相应的未取代的吡啶-1-酰胺和二硫代羧酸甲酯为原料,制备了吡啶-1-酰胺、2-甲基吡啶-1-酰胺和 2,6-二甲基吡啶-1-硫代羧酸酰胺(5-7),收率相当高。5-7 的烷基化反应完全发生在硫代羰基硫上,定量生成吡啶鎓盐。核磁共振光谱研究表明,这些吡啶鎓盐存在 E 和 Z 两种形式。5-7 的热分解产生了相应的吡啶、腈和硫,收率很高。
Preparation of New Nitrogen-bridged Heterocycles. 11. A New Synthetic Method of Pyrazolo[1,5-<i>a</i>]pyridines from the Alkaline Treatment of 1-[(Acylmethylthio)methyleneamino]pyridinium Salts
Alkaline treatment of 1-[(acylmethylthio)methyleneamino]pyridinium halides gave unexpectedly 3-acyl- or 3-(acylthio)pyrazolo[1,5-a]pyridine derivatives in 35–87% yields. Some 4,4a-dihydropyrido[1,2-d][1,3,4]thiadiazine intermediates involved in these reactions could be detected by their nmr follows and three related 4a,8-dimethyl derivatives were isolated. Substituent effect and possible mechanisms
benzylthio)methyleneamino]pyridinium and 1-[2-(substituted benzylthio)vinyl]pyridinium bromides possessing an electron-withdrawing substituent such as a nitro or cyano group in the presence or absence of a dehydrogenating agent afforded the corresponding 3-arylpyrazolo[1,5-a]pyridines and 1-arylindolizines in moderate to good yields, while the reactions of the parent pyridiniumsalts and those having an