Comparative reactivity of exo- and endo-isomers in the ru-initiated ring-opening metathesis polymerization of doubly functionalized norbornenes with both cyano and ester groups

A comparative study was conducted on the exo- and endo-isomers in the Ru-initiated ring-opening metathesis polymerization (ROMP) of doubly functionalized norborenes with both cyano and ester groups. Isometrically pure endo-form B and doubly functionalized exo-ethyl 3-cyanobicyclohept-5-ene-2- carboxylate (A)were prepared. The ROMP of exo-isomer A and endo-isomer B and the parent norborene were studied using the second-generation Grubbs' catalyst. The IR spectra of all the polymers obtained were very similar, while signals characteristics of the cyano group and ester carbonyl group at 2304 and 1734 cm^-1, respectively, were prominent features of the spectra. Compared to the parent norborene, cyano and ester functional groups seem to have an interaction with the Ru center, suppressing the polymerization.