Bx. Wang et al., The aromatization of Hantzsch 1,4-dihydropyridines by tetrakis-pyridine cobalt (II) dichromate (TPCD), SYN COMMUN, 29(23), 1999, pp. 4193-4199
Aromatization of Hantzsch 1,4-dihydropyridines (1a-n) were promoted by tetr
akis-pyridine cobalt (II) dichromate to yield corresponding pyridine deriva
tives (2a-n) in moderate to high yields (70-87%). The reaction was carried
out under mild and convenient conditions.