The effect of lithium iodide on the acid-promoted cyclization of 4-[(1-indolylcarbonyl)methyl]-1,4-dihydropyridines

Article abstract of DOI:10.1016/0040-4039(96)01703-0

1,4-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.