Synthesis and resolution of 2,2'-bis-diphenylphosphino [3,3']biindolyl; a new atropisomeric ligand for transition metal catalysis

Article abstract of DOI:10.1016/0957-4166(95)00447-5

A synthesis of the title ligand is described in which the key step is the dilithiation of 1,1'-bis(dimethylaminomethyl)-3,3'-biindolyl and electrophilic trapping with ClPPh₂. Concomitant N-deprotection and resolution with bis[(R)-dimethyl(1-(1-naphthyl) ethylaminato-C²,N)palladium chloride] led to selective recovery of the S-enantiomer. The N-dimethylaminomethyl-substituted biindolyl, but not the parent compound, showed strongly second-order behaviour for ¹³C NMR peaks in the region of the phosphorus atom due to a desymmetrising ¹³C-induced isotope shift of the ³¹P resonance.