Utilization of optically active secondary phosphine-boranes: synthesis of P-chiral diphosphines and their enantioinduction ability in rhodium-catalyzed asymmetric hydrogenation

摘要

Both enantiomers of tert-butylmethylphosphine-borane have been used for the synthesis of P-chiral diphosphines and/or their borane complexes. The enantiopure borane complex of 1,2-bis(tert-butylmethylphosphino)ethane (t-Bu-BisP*) was prepared in high yield from the secondary phosphine-borane and 1,2-dichloroethane. A mono-chelated Rh-complex of t-Bu-MiniPHOS was prepared and its catalytic activity was examined in the asymmetric hydrogenation of some representative functionalized alkenes. Synthesis of three new P-chiral phosphine ligands with quinoline or quinoxaline backbone is also described together with their enantioinduction ability. (C) 2015 Elsevier Ltd. All rights reserved.