Development of Transition Metal Catalysts with Optical Active [2.2] Paracyclophanebisphosphine Ligands

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Our initial plan to synthesize the [2.2]paracyclophanebisphosphine ligand was to dimerize a bridged bis(p-xylylene) intermediate to realize the desired pseudo-ortho disubstitution selectively. Although the precursor of the reaction intermediate was prepared smoothly via a newly developed route, the intramolecular version of the dimerization failed, possibly due to difficulty of generating the bis(p-xylylene) intermediate.While we were examining the reaction conditions for selective introductionm of two bromine atoms in a pseudo-ortho fashon, exactly the same project dealing with the synthesis and catalytic activity of [2.2]paracyclophanebisphosphine- ruthenium and palladium complexes was reported by a Merck research group in U.S.A.However, the bottleneck of their synthetic route was the tedius separation of the pseudo-ortho dibromide from a complex mixture of bromination products. In our preliminary studies, both theoretically and expermentally, we arrived at the conclusion that gas-solid reaction between bromine vapor and powdered [2.2]paracyclophane would be pseudo-ortho selective. Improvement of the rection conditions is now underway.As the related C2 chiral cyclophane ligands, we succeeded in the synthesis and resolution of bidentate nitrogen ligands derived from cyclic Tr_ger bases.