Phanephos
Phanephos is an organophosphorus compound with the chemical formula (CH)(CHPPh) (Ph = CH). It is a white solid that is soluble in organic solvents. It is an example of a chiral C-symmetric diphosphine ligand used in asymmetric hydrogenation. Many substituents have been introduced in place of the phenyl groups, e.g., "i"-Pr, CH, etc and a variety of chiral diphosphine ligands have been reported in asymmetric catalysis since the 1960s. Preparation. Phanephos can be prepared in two steps from [2.2]paracyclophane. In the first step, [2.2]paracyclophane is dibrominated to give a pseudo-para dibromide. Thermal isomerisation then gives pseudo-ortho  atropisomer of the dibromide. This isomer is subjected to lithium-halogen exchange by nBuLi and the resulting dilithium compound is treated with PPhCl to give a racemic mixture of Phanephos. Uses. Phanephos has been used in rhodium- and ruthenium- mediated stereoselective hydrogenation of dehydro amino acid methyl esters and asymmetric reduction of various β-ketoesters with about 90 % ee.