Ru-based Grubbs catalysts employed in cyclopolymerization (CP) of diyne deivatives have promoted selective α-addition, forming the conjugated polyenes containing exclusively five-membered repeat unit in the case of 1,6-heptadiynes. Along with our recent achievement on β-selective CP using a Ru Z-selective olefin metathesis catalyst, we have pursued a higher efficiency and more selective regiocontrol to produce conjugated polymers with only six-membered rings with broader substrate scope. Herein, we demonstrate a very β-selective CP by applying another type of Ru-based Z-selective dithiolate catalyst, and discovering the prominent effects of pyridine additives to improve the conversion and the selectivity. In-depth observation and monitoring on the reactive carbene species enabled us to understand the plausible role of pyridine ligands, such as stabilizing the propagating carbenes and control ki/kp values. All of the investigation led the living/controlled CP and further diblock copolymerization to be possible, which became the first example for CP in a completely β-selective and living manner using Ru-based catalysts.

β–selective cyclopolymerization using Ru-dithiolate olefin metathesis catalysts by controlled manner

256th National Meeting (2018)

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