Synthesis and Resolution of a New Type of Chiral Bisphosphine Ligand, trans‐Bis‐ 1,2‐(diphenylphosphino)cyclobutane, and Asymmetric Hydrogenation Using Its Rhodium Complex.

Oxidative coupling of the 1,4-dicarbanions derived from bis-1,4-(diphenylphosphinyl)butane gave (±)-trans-bis-1,2-(diphenylphosphinyl)cyclobutane. Asymmetric hydrogenation of dehydroamino acids using rhodium complex of the optically active bisphosphine obtained by reduction of the resolved bisphosphine oxide afforded hydrogenated products in high optical yields.