Enantioselective organocatalytic reductions

The enantioselective organocatalytic methodologies described in this chapter are a clear demonstration of the enormous potentiality of metal-free catalytic reductions. Despite the historical need for and continued interest in chiral amines, their synthesis remains challenging. In one case, binaphthol-derived phosphoric acids have been successfully employed in a process that involves the use of a dihydropyridine-based compound as the reducing agent. In another strategy the reducing agent is trichlorosilane; finally in the very last few years a novel approach has been developed to realize metal-free hydrogenation of imines: The Frustrated Lewis Pair (FLP) method involves the use of a combination of a strong Lewis acid with a variety of sterically encumbered Lewis bases to activate hydrogen at ambient conditions. It is recognized that these chemical adducts could find application in catalytic hydrogenation reactions.