1577-22-6Relevant articles and documents
Application of a metathesis reaction in the synthesis of sterically congested medium-sized rings. A direct ring closing versus a double bond migration-ring closing process
Michalak, Michal,Wicha, Jerzy
, p. 3439 - 3446 (2011)
An efficient double bond migration-ring closing metathesis reaction leading to cycloheptene derivatives is observed when specific sterically congested 1,9-dienes are treated with the Grubbs' imidazolidene ruthenium catalyst. The simultaneous use of the Grubbs' catalyst and RuClH(CO)(PPh3) 3 facilitates the tandem bond migration-metathesis process. RuClH(CO)(PPh3)3 alone is capable of triggering an unactivated double bond migration that may have preparative applications.
On the Mechanism of the Ethyl Elimination from the Molecular Ion of 6-Methoxy-1-Hexene
Molenaar-Langeveld, Tineke A.,Fokkens, Roel H.,Nibbering, Nico M. M.
, p. 364 - 369 (1988)
It is shown by 13C and D labelling that the ethyl radical elimination from the molecular ion of 6-methoxy-1-hexene is a very complex process involving at least two different channels.The major channel (80percent) is induced by an initial 1,5-hydrogen shift in the molecular ion from C(5) to C(1) leading via a series of steps to methoxycyclohexane, which then undergoes a ring contraction to 2-methyl-1-methoxycyclopentane, being the key intermediate for the ethyl loss.The same key intermediate is formed in the other, minor channel (20percent) by ring closure directly following an initial 1,6-hydrogen shift in the molecular ion of 6-methoxy-1-hexene from C(6) to C(1).Collision-induced dissociation experiments on the + ion from 6-methoxy-1-hexene have further established that it has the unique structure of oxygen methyl cationized 2-methylpropen-2-al.This ion is also generated by ethyl loss from the molecular ion of 2-methyl-1-methoxycyclopentane itself, as shown by collision-induced dissociation experiments, thus confirming the key role of the intermediate mentioned.
Accelerated Semihydrogenation of Alkynes over a Copper/Palladium/Titanium (IV) Oxide Photocatalyst Free from Poison and H2 Gas
Imai, Shota,Nakanishi, Kousuke,Tanaka, Atsuhiro,Kominami, Hiroshi
, p. 1609 - 1616 (2020/02/15)
Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core-Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two-step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. Thus-prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4-octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4-Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4-octyne was semihydrogenated to cis-4-octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4-octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed.
Highly active bidentate N-heterocyclic carbene/ruthenium complexes performing dehydrogenative coupling of alcohols and hydroxides in open air
Wang, Zhi-Qin,Tang, Xiao-Sheng,Yang, Zhao-Qi,Yu, Bao-Yi,Wang, Hua-Jing,Sang, Wei,Yuan, Ye,Chen, Cheng,Verpoort, Francis
supporting information, p. 8591 - 8594 (2019/07/25)
Eight bidentate NHC/Ru complexes, namely [Ru]-1-[Ru]-8, were designed and prepared. In particular, [Ru]-2 displayed extraordinary performance even in open air for the dehydrogenative coupling of alcohols and hydroxides. Notably, an unprecedentedly low catalyst loading of 250 ppm and the highest TON of 32 800 and TOF of 3200 until now were obtained.