Monosubstituted aliphatic acetylenes such as cholesteryl 3-butynyl carbonate (1 a) and cholesteryl 6-heptynyl carbonate (1 d) were synthesized and polymerized with a Rh(nbd)[B(C6H5)4] (nbd: norbornadiene) catalyst in tetrahydrofuran to give soluble polymers in almost quantitative yields. Poly(1 a), which was found to be composed of a cis structure in the main chain by NMR analysis, showed intense circular dichroism (CD) in the UV/Vis region assigned to the π-π* transition of the helical main chain induced by the cholesteryl side group, while poly(1 d) contains both cis and trans structure in the main chain without showing significant CD. Poly(1 a) was not deteriorated in air after a month, although the cis to trans isomerization was observed to take place by annealing, together with the intramolecular trimerization of the main chain.
No takes yet. Share an insight, caveat, or question.
Mitsuyama et al. (2000) studied this question.