Kang Cheol, Sung Jong-Chan, Kim Kunsoon, Hong Soon Hyeok, Choi Tae-Lim
Department of Chemistry, Seoul National University, Seoul, 08826, Republic of Korea.
Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea.
ACS Macro Lett. 2020 Mar 17;9(3):339-343. doi: 10.1021/acsmacrolett.9b00986. Epub 2020 Feb 19.
Cascade metathesis and metallotropy (M&M) polymerization, which involves sequential olefin metathesis and metallotropic 1,3-shift reactions specifically from multiyne monomers, is the only method reported so far to prepare conjugated polyenynes via the chain-growth mechanism. Using this method, various conjugated polyenynes containing cyclopentene units in the backbone could be synthesized via exclusive α-addition by using the third-generation Grubbs catalyst. Herein, we demonstrate the complete switch of regioselectivity toward β-addition using a Ru carbene containing a dithiolate ligand, and thus, synthesized unique conjugated polyenynes having alternating cyclohexene and cyclopentene units in the backbone. Furthermore, detailed in situ NMR studies revealed an interesting phenomenon that the adjacent triple bond strongly chelates to the propagating Ru carbene during the polymerization.
级联复分解和金属转移（M&M）聚合反应涉及特定的多炔单体依次进行烯烃复分解和1,3-金属转移反应，是迄今为止报道的唯一一种通过链增长机制制备共轭多烯炔的方法。使用这种方法，通过使用第三代格拉布催化剂进行专一的α-加成，可以合成主链中含有环戊烯单元的各种共轭多烯炔。在此，我们展示了使用含有二硫醇盐配体的钌卡宾实现区域选择性向β-加成的完全转变，从而合成了主链中具有交替环己烯和环戊烯单元的独特共轭多烯炔。此外，详细的原位核磁共振研究揭示了一个有趣的现象，即在聚合过程中相邻的三键与增长的钌卡宾强烈螯合。
