Living/controlled cyclopolymerization (CP) of 1,7-octa- and 1,8-nonadiyne derivatives was achieved by novel design of diyne monomers. Especially, the CP of 1,8-nonadiynes forming challenging medium-sized seven-membered rings was the first example. The key to the successful CP was the introduction of appropriate heteroatoms: i) hydrazide groups, which have two protecting groups, resulting in increased Thorpe-Ingold effect and ii) aminal and acetal groups, which have short C-N and C-O bonds, and low rotational barriers. During our mechanistic investigation into the CP of 1,8-nonadiyne derivatives, we observed a same Ru propagating carbene from two respective polymerizations using 2nd generation Hoveyda-Grubbs catalyst and 3rd generation Grubbs catalyst (GIII) by 1H NMR spectroscopy. This Ru propagating carbene was isolated and turned out to be a bottom-bound isomer of olefin-bound Ru carbene by X-ray crystallography. Finally, we achieved a controlled CP of the aminal monomers using a fast-initiating GIII with the aid of stable olefin-bound Ru propagating carbene. This allowed the synthesis of not only the diblock copolymer containing five- and seven-membered rings, but also the triblock copolymer containing five-, six-, and seven-membered rings.

Six- and seven-membered ring-forming cyclopolymerization of various diyne derivatives using Grubbs catalysts: Rational design of monomers and direct observation of propagating carbene

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.