Highly Enantiomer-Selective And Helix-Sense-Controlled Synthesis Of Stereoregular Helical Polycarbenes Using Chiral Palladium(?) Catalysts

In recent years,researchers have made great achievements in the polymerization of diazo monomers,but the problems of enantiomer-selective and helix-sense-controlled polymerization of diazo monomers are still difficult for scholars and experts.We have studied enantioselective and helix-sense-controlled polymerization of diazoacetate enantiomers bearing R-or S-methylbenzyl ester(1r or 1s)substituent by a chiral allyl Pd C l/L~R catalyst.The polymerisation afforded well-defined polycarbenes with controlled molecular weights and narrow molecular weight distributions.Remarkably,these polymers exhibited unexpectedly high stereoregularit y as revealed by NMR studies.Moreover,the polymerization showed high enantiomer-selectivity on the polymerization of the two enantiomers.The polymerization rate of the two enantiomers can be up to 130 times difference,albeit the chiral centre is remote from the polymerization site.Interestingly,the isolated polymers showed high optical activity due to the formation of one-handed preferred helix of the main chain as revealed by circular dichroism and absorption spectra,and directly atomic force microscope observation as well.Moreover,Synthetic polycarbene has great application prospects in the biological field and high-tech fields,such as biological probes,chiral separation materials,photosensitive materials,and so on.