silicon-initiated cascade carbonylativecarbotricyclization (CO-SiCaT) process. It has also been found that the 5-7-5 fused tricyclic products can be obtained from the same type of enediynes and CO through a novel intramolecular [2+2+2+1] cycloaddition process. The characteristics of these two tricyclization processes and the fundamental differences in their reaction mechanisms are discussed. This novel higher-order
Versatile Tandem Ring-Opening/Ring-Closing Metathesis Polymerization: Strategies for Successful Polymerization of Challenging Monomers and Their Mechanistic Studies
electronic effects of the alkyne substituents influenced alkyne addition selectivity and the polymerization reactivity. Further polymerization kinetics studies revealed that the rate-determining step of monomers containing certain internal alkynes was the six-membered cyclization step via β-addition, whereas that for other monomers was the conventional intermolecular propagation step, as observed in other
Cyclization of 1,<i>n</i>-Enynes Initiated by the Addition Reaction of <i>gem</i>-Dichromiomethane Reagents to Alkynes
作者:Masahito Murai、Ryuji Taniguchi、Kazuhiko Takai
DOI:10.1021/acs.orglett.0c01304
日期:2020.5.15
Treatment of 1,n-enynes with gem-dichromiomethane species prepared in situ from 1,1-diiodomethanes and CrCl2 gave alkenylbicycloalkanes. Alkenylcarbene species, which was generated via [2 + 2] cycloaddition with a triple bond, were intercepted by intramolecular cyclopropanation of a pendant double bond, and alkene metathesis did not proceed. This is a very rare example of transformation of alkynyl
Nickel-catalyzed coupling of allyl chlorides and enynes
作者:Shin-ichi Ikeda、Kaori Suzuki、Kazunori Odashima
DOI:10.1039/b515508h
日期:——
The Ni-catalyzed coupling of allyl chlorides and enynes has been developed; the cyclization of enynes was triggered by the addition of π-allylnickel species to the alkyne part, followed by the incorporation of the alkene part.
A Ni(O)/ZnCl2 system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(O) species on enones across the alkyne part followed by ZnCl2-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting sigma-alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyclopentane derivatives. On the other hand, a sigma-alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the cleavage of one C-C bond.