Understanding the Origin of the Regioselectivity in Cyclopolymerizations of Diynes and How to Completely Switch It

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Title
Understanding the Origin of the Regioselectivity in Cyclopolymerizations of Diynes and How to Completely Switch It
Author(s)
Hoimin Jung; Kijung Jung; Mannkyu Kwon; Seongyeon Kwon; Kunsoon Kim; Soon Hyeok Hong; Tae-Lim Choi; Mu-Hyun Baik
Publication Date
2018-01
Journal
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, v.140, no.2, pp.834 - 841
Publisher
AMER CHEMICAL SOC
Abstract
Grubbs-type olefin metathesis catalysts are known to cyclopolymerize 1,6-heptadiynes to afford conjugated polyenes containing five- or six-membered carbocycles. Although high levels of regioselectivity up to >99:1 were observed previously for the formation of five-membered rings, it was neither possible to deliberately obtain six-membered rings at similar levels of selectivity nor understood why certain catalysts showed this selectively. Combining experimental and computational methods, a novel and general theory for what controls the regiochemistry of these cyclopolymerizations is presented. The electronic demands of the ruthenium-based Fischer carbenes are found to innately prefer to form five-membered rings. Reducing the electrophilicity of the carbene by enforcing a trigonal-bipyramidal structure for the ruthenium, where stronger π-backdonation increases the electron density on the carbene, is predicted to invert the regioselectivity. Subsequent experiments provide strong support for the new concept, and it is possible to completely switch the regioselectivity to a ratio of <1:99. © 2017 American Chemical Society
URI
https://pr.ibs.re.kr/handle/8788114/4745
ISSN
0002-7863
Appears in Collections:
Center for Catalytic Hydrocarbon Functionalizations(분자활성 촉매반응 연구단) > Journal Papers (저널논문)
Files in This Item:
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