A new approach to Bronsted acid organocatalysis is described and is based on the use of thiophosphonic acids possessing both a chiral backbone and a chiral phosphorus function. The influence of the phosphorus stereochemistry on the enantioselectivity proved to be crucial in the hydrogentransferhydrogenation of 2-phenylquinoline with Hantzsch esters.
An improved strategy for the synthesis of P-chiral gluco- and manno-phosphonite-borane complexes is described on the basis of the addition of diethyl phosphonite-borane to a glucal-derived aldehyde, followed by a cyclization coupled with an ethyl/methyl exchange. This direct P(III) strategy facilitates the obtention of various P-chiral phosphonite-boranes, of which further coupling reactions are described leading to the selective synthesis of two phostone dimers.