Old Reagents, New Results: Aromization of Hantzsch 1,4-Dihydropyridines with Manganese Dioxide and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone.

Article abstract of DOI:10.1016/0040-4020(95)00318-3

Hantzsch 1,4-dihydropyridines are readily oxidized by manganese dioxide or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in dichloromethane at room temperature.With manganese dioxide loss of the 4-substituent, in addition to aromatization, occurs when i