2,4-Bismethylthiopyridinium iodides prepared from 2(1 H)-pyridinethiones react regioselectively with active methylene compounds, preferentially at the 4-position, yielding 4-alkylidene-1,4-dihydropyridines. The corresponding 4-benzylthio-2-methylthiopyridinium iodide gave a mixture of 2-alkylidene-1,2-dihydro- and 4-alkylidene-1,4-dihydropyridines. By treatment with phosphoric acid, the resulting new 3-acetyl-2-alkyliden-1,2-dihydro- and 4-alkylidene-1,4-dihydropyridines yielded 1,6- and 2,7-naphthyridines, respectively.
2,4-双甲基
硫代
吡啶鎓
碘化物由2(1 H)-
吡啶硫酮制备,与活性亚甲基化合物进行位点选择性反应,优先在4位上反应,生成4-亚甲基-1,4-
二氢吡啶。相应的4-苄
硫基-
2-甲硫基吡啶鎓
碘化物生成2-亚甲基-1,2-
二氢吡啶和4-亚甲基-1,4-
二氢吡啶的混合物。通过
磷酸处理,生成新的3-乙酰基-2-亚甲基-1,2-
二氢吡啶和4-亚甲基-1,4-
二氢吡啶,分别生成1,6-和
2,7-萘啶。