What is "binap"

BINAP (2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) is an organophosphorus compound. This chiral ligand is widely used in asymmetric synthesis. It consists of a pair of 2-diphenylphosphino naphthyl groups linked at the 1 and 1´ positions. This C-symmetric framework lacks a stereogenic atom, but has axial chirality due to restricted rotation ( atropisomerism). The barrier to racemization is high due to steric hindrance, which limits rotation about the bond linking the naphthyl rings. The dihedral angle is approximately 90˚.