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

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 Cl(P)Ph(2). Concomitant N-deprotection and resolution with bis[(R)-dimethyl(1-(1-naphthyl) ethylaminato-C-2,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 C-13 NMR peaks in the region of the phosphorus atom due to a desymmetrising C-13-induced isotope shift of the P-31 resonance.