A new route to chiral bis-tertiary phosphine ligands: synthesis, resolution, and crystal structure of trans-bis-1,2-(diphenylphosphino)-cyclopentane and the nickel adduct NiBr2[trans-1,2-(PPh2)2C5H8]

Abstract

Heating of white phosphorus, phosphorus trichloride, and cyclopentene at 220 °C gives trans-1,2-bis (dichlorophosphino)cyclopentane (1), which with phenylmagnesium bromide gives trans-1,2-bis(diphenylphosphino)-cyclopentane (dpcp)(2); compound (2)forms the adduct Ni(dpcp) Br₂·CH₂Cl₂, which readily crystallizes as a conglomerate and the pure enantiomers may be separated by hand allowing resolution of (2), and catalytic hydrogenation of methyl(N-benzoyl) dehydrophenylalanine using resolved (2)and a rhodium catalyst gave a hydrogenated product of 100% optical purity.