Enantioselective polymerization of (R,S)‐α‐methylbenzyl methacrylate initiated with products resulting from grignard reagents and axially dissymmetric [1,1′‐binaphthyl]‐2,2′‐diamine

Enantioselective polymerization of ( R , S )‐α‐methylbenzyl methacrylate [( R , S )‐ 3 ] was investigated in tolurene at −30°C with a variety of chiral anionic catalysts, prepared in situ by reaction of axially dissymmetric [1,1′‐binaphthyl]‐2,2′‐diamine ( 1 ) and Grignard reagents (RMgX, R = alkyl). The enantioselectivity was found to be dependent upon the halogen ions of RMgX, but scarcely upon the alkyl groups. The catalyst systems involving ( R )‐ 1 polymerize more or less preferentially ( S )‐ 3 over ( R )‐ 3 . The selectivity is also discussed with respect to the mole ratio of RMgX to 1 . The system cyclohexylmagnesium bromide ( c HexMgBr)/( R )‐ 1 , in a mole ratio of 1,5:1,0, shows high selectivity, and the optical purity of the initially formed polymer was found to reach 83%. The change in the optical purities of polymer and unreacted monomer can be represented satisfactorily by the integrated composition equation for an “ideal” copolymerization of ( R )‐and ( S )‐monomers, and the enantioselectivity ratio, r , was estimated to be 10,6. The polymers produced are almost completely isotactic, and contain a binaphthyl moiety as initiator fragment.