The dearomatization of N-heteroarenes to afford dihydropyridines (DHPs) is an important transformation as it provides a pathway to a range of substrates which are biologically useful agents e.g. nicotinamide adenine dinucleotide (NADH), and in the synthesis of pharmaceutically important drug molecules. Moreover, 1,4-DHPs are also known to serve as reducing agents in organocatalysis by functioning as organohydride donors, and are also products of the multicomponent Hantzch ester synthesis which are of potential use as NADH mimics. Thus, a range of methods have been reported which allow synthetic access to DHPs, though achieving regioselectivity remains a challenge. Preliminary work established that combinations of Ni(acac)2 with phosphine ligands were found to catalyze the regioselective hydroboration of N-heteroarenes with pinacolborane, affording N-borylated 1,4-reduction products. We now present work to extend this transformation to chiral phosphines and NHC ligands and report on mechanistic studies which have focused on the isolation and study of potential intermediates in the catalytic cycle.

Nickel catalyzed 1,4 -selective hydroboration of pyridines and N-heteroarenes

256th National Meeting (2018)

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