Mechanism of 1-phenyl-1,4-dihydropyridine formation in reaction of 1-phenylpyridinum chloride with alkali metal alkoxides

Quaternary salt Ia reacts with sodium and lithium alkoxides to give 1-phenyl-1,4-dihydropyridine (IIIa) together with unsaturated aldehyde IVa. The reaction mechanism for formation of compound IVa from the primarily arising 2-alkoxy-1-phenyl-1,2-dihydropyridines is suggested on the basis of products IIIb and IVb, arising from the 3,4,5-trideuterio precursor Ib.