Substituted Dihydropyridine Synthesis by Dearomatization of Pyridines.

Dearomatization is an effective method to transform readily available N-heterocycles into partially saturated motifs. Manipulation of dihydro-derivatives holds great potential and provides access to a variety of semi-saturated N-heterocyclic building blocks. However, current strategies are limited in scope and the use of sensitive reagents restricts the applicability in synthetic laboratories. In this work, we report the synthesis of a broad variety of N -substituted 1,4- and 1,2-dihydropyridines by very mild and selective reduction with amine borane for the first time.