Synthesis and reactions of phosphine-boranes. Synthesis of new bidentate ligands with homochiral phosphine centers via optically pure phosphine-boranes

Article abstract of DOI:10.1021/ja00169a036

Secondary and tertiary phosphine-boranes were synthesized in one-pot from phosphine oxides or substituted chlorophosphines without isolation of the intermediate phosphines. Phosphine-boranes having a methyl group were metalated with sec-butyllithium. The generated carbanions reacted with alkyl halides or carbonyl compounds to yield various phosphine-borane derivatives. The carbanions underwent copper(II)-promoted oxidative coupling without impairment of the borane functionality. Secondary phosphine-boranes reacted with alkyl halides, aldehydes, or α,β-unsaturated carbonyl compounds to give phosphine-borane derivatives having a functional group. The boranato group of phosphine-boranes was removed in a stereospecific manner with retention of configuration by treatment with a large excess of amine such as morpholine. A new route to bidentate ligands with homochiral phosphine centers has been explored by utilizing these characteristic reactivities of phosphine-boranes. Thus, optically pure (S,S)-1,2-bis(o-anisylphenylphosphino)ethane, (R,R)-1,2-bis(tert-butylphenyl-phosphino)ethane, and (S,S)-1,4-bis(o-anisylphenylphosphino)butane have been synthesized via phosphine-boranes.