Synthesis and first applications of a new family of chiral monophosphine ligand: 2,5-diphenylphosphospholanes

The cyclic phosphinic acid 1-hydroxy-1-r-oxo-2c,5-t-diphenylphospholane was synthesized and resolved into enantiomers through fractional crystallization of the quinine salts. The P-phenyl, P-methyl and P-benzyl tertiary phosphine oxides were obtained from the secondary phosphine oxide, reduction of the oxides afforded the corresponding tertiary P-phenyl and P-benzyl phosphines. Hydrogenation of prochiral enamides were performed with Rh/(S,S)-1-1,2c,5-t-triphenylphospholane catalytic system. Methyl (Z)-N-acetyl dehydrocinnamate was hydrogenated to give the N-acetyl phenylalaninate in 93% ee.