Aromatization of Hantzch 1,4-dihydropyridines was achieved under radical cation salt induced conditions, in which triarylamine radical cation acts as an efficient catalyst to prompt the aerobic oxidation of 1,4-DHPs in a catalytic way.

A simple adaptation allows batch protocols developed using microwave heating that involve formation of solid organic products to be scaled up using conventionally-heated flow chemistry with minimal or no re-optimization or modification. The product stream is intercepted with a flow of a suitable organic solvent upon exiting the heated zone, this solubilizing the product and allowing it to pass through the back-pressure regulator without aggregation of particulate material.