Reactions of biologically inspired hydride sources with B(C(6)F(5))(3)

The combination of 1-benzyl-1,4-dihydropyridines with the strong Lewis acid, B(C(6)F(5))(3), generates a stable pyridinium borohydride species in high yields (94%) in as little as 10 min. This use of biologically inspired hydride sources further builds on the recent work of new hydride donors in the formation of borohydrides. When functionalizing the dihydropyridine with an amide or carboxylic acid moiety, a disproportionation reaction composed of a series of protonation/reduction steps is observed upon the addition of B(C(6)F(5))(3). As a result, one equivalent of dihydropyridine undergoes net hydrogenation, whereas the other is dehydrogenated yielding the pyridinium counterpart in a transfer hydrogenation-type mechanism. This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.