4-Dihydropyridines 3 resulting from the addition of the enolate derived from 1-acetylindole (1) to pyridinium salts 2 do not undergo cyclization under the usual acidic conditions, but do satisfactorily cyclize to the tetracyclic derivatives 4 by treatment with TsOH in the presence of lithium iodide.
                                    由1-乙酰基
吲哚(1)衍生的烯醇化物加到
吡啶鎓盐2中而得到的1,4-
二氢吡啶3在通常的酸性条件下不进行环化,但通过在TsOH中进行TsOH处理,可以令人满意地环化为四环衍
生物4。
碘化
锂的存在。