Benzimidazoline hydride transfer

Nature makes use of NADH (reduced nicotinamide adenine dinucleotide) as a cofactor for enantioselective biochemical hydrogenations, which are typical hydride-transfer reactions. Dihydropyridines and benzimidazolines derivatives are active hydride donors due to the presence of the nitrogen atom and the ability of the molecule to undergo aromatisation. Organocatalytic enantioselective reductions carried out using hydride donors has been studied, and effective reductions have been achieved with imidazoli-dinone organocatalysts, both with a,p unsaturated aldehydes and ketones. Generally, a stoichiometric quantity of reductant (Hantzsch ester 4) is required for these transformations (Scheme 18.5). 

---