Highly efficient and practical optical resolution of 2-amino-2'-hydroxy- 1,1'-binaphthyl by molecular complexation with N-benzylcinchonidium chloride: A direct transformation to binaphthyl amino phosphine

A new type of N,P chiral ligand, binaphthyl amino phosphine 1 was synthesized through a simple and practical resolution of racemic 2-amino-2'- hydroxy-1,1'-binaphthyl by molecular complexation with 0.5 equivalents of N- benzylcinchonidium chloride in the solid state. The present procedure represents the first example of the optical resolution of amino alcohol with the use of a chiral ammonium salt as a resolving reagent. The resolution mechanism is discussed in terms of molecular recognition in solid state. The chlorine anion in N-benzylcinchonidium chloride provides the bridging link between two amino alcohol molecules [(+)-2] and the cinchonoid cation located in between, by hydrogen bonding with the surrounding moieties.