An Improved and Safer Synthesis of (R)- and (S)-4,4'-Diaminomethyl-BINAP

(R)- and (S)-4,4'-diaminomethyl-BINAP were prepared in three steps from enantiomerically pure BINAPO in a global yield of 52?%. A regioselective bromination of BINAPO with NBS in HMimPF6 gave the desired 4,4'-dibromo-BINAPO in quantitative yield, and the recyclability of the ionic liquid was demonstrated. Copper cyanide cyanation of 4,4'-dibromo-BINAPO gave the 4,4'-dicyano-BINAPO in 70?% yield. Both enantiomers were characterized by NMR spectroscopy and HPLC analysis, and the structures were confirmed by X-ray crystallography. The cyano and phosphane oxide groups of the resulting 4,4'-dicyano-BINAPO were reduced in one step to the corresponding 4,4'-diaminomethyl-BINAP by using tetramethyldisiloxane/Ti(OiPr)4 in 75?% yield.