New optically active organoantimony (BINASb) and bismuth (BINABi) compounds comprising a 1,1′-binaphthyl core: synthesis and their use in transition metal-catalyzed asymmetric hydrosilylation of ketones

Abstract

Racemic 2,2′-bis[diarylstibano]-1,1′-binaphthyls [(±)-BINASbs] and 2,2′-bis[di( p-tolyl)bismuthano]-1,1′-binaphthyl [(±)-BINABi], which are the antimony and bismuth congeners of BINAP, have been prepared from 2,2′-dibromo-1,1′-binaphthyl (DBBN) via 2,2′-dilithio-1,1′-binaphthyl intermediate by treatment with the appropriate metal halides [( p-Tol) 2SbBr, Ph 2SbBr and ( p-Tol) 2BiCl]. The optical resolution of the (±)-BINASbs could be achieved via the separation of a mixture of the diastereomeric Pd-complexes derived from the reaction of (±)-BINASbs with di-μ-chlorobis{( S)-2-[1-(dimethylamino)-ethyl]phenyl- C 1, N}dipalladium(II). Optically active ( R)-BINASb and ( R)-BINABi could be also obtained from optically active ( R)-DBBN by the same procedure. The enantiopure BINASbs have been shown to be effective chiral ligands for the rhodium-catalyzed asymmetric hydrosilylation of ketones.