25498-06-0Relevant articles and documents
Kinetics of the Thermal Isomerizations of Gaseous Cycloheptene and Cyclooctene
Kalra, Bansi L.,Afriyie, Yau,Brandt, Benjamin,Lewis, David K.,Baldwin, John E.
, p. 8142 - 8146 (1995)
Single-pulse shock tube kinetic studies of the thermal isomerizations of gaseous cycloheptene (CHEP) and cis-cyclooctene (COCT), and static reactor isomerizations of COCT at lower temperatures, have revealed a mechanistic dissimilarity in the two superficially analogous cycloalkene to, α,ω-alkadiene reactions observed.At 1035-1256 K, CHEP produced mostly vinylcyclopentane, log10(k,s-1) = 15.1 (+/- 0.7) - 69.7 (+/- 3.3) x 103/4.576T, and some 1,6-heptadiene.From COCT, heated over the range 610-1091 K, the dominant product was 1,7-octadiene, log10(k,s-1) = 13.8 (+/- 0.2) -54.6 (+/- 0.5) x 103/4.576T, with small amounts of vinylcyclohexane formed at the higher temperatures, log10(k,s-1) = 15.2 (+/- 0.3) - 64.4 (+/- 1.2) x 103/4.576T.The activation energy for the COCT isomerization to 1,7-octadiene is too low to associate with formation of a diradical, but is consistent with a concerted retro-ene mechanism.The higher activation energy isomerization to vinylcyclohexane, however, passes through a diradical transition structure.In contrast, the structure of CHEP is not adaptable to a concerted retro-ene precess, and both 1,6-heptadiene and vinylcyclopentane are formed through diradical-mediated reactions.
Contra-thermodynamic Olefin Isomerization by Chain-Walking Hydroboration and Dehydroboration
Bloomer, Brandon,Butcher, Trevor W.,Ciccia, Nicodemo R.,Conk, Richard J.,Hanna, Steven,Hartwig, John F.
, p. 1005 - 1010 (2022/02/10)
We report a dehydroboration process that can be coupled with chain-walking hydroboration to create a one-pot, contra-thermodynamic, short-or long-range isomerization of internal olefins to terminal olefins. This dehydroboration occurs by a sequence comprising activation with a nucleophile, iodination, and base-promoted elimination. The isomerization proceeds at room temperature without the need for a fluoride base, and the substrate scope of this isomerization is expanded over those of previous isomerizations we have reported with silanes.
Norrish type II reactions of acyl azolium salts
Hopkinson, Matthew N.,Mavroskoufis, Andreas,Rieck, Arielle
, (2021/10/25)
The photochemical reactivity of acyl azolium salts derived from aliphatic carboxylic acids has been investigated. These species, which serve as models for intermediates generated in N-heterocyclic carbene (NHC) organocatalysis, undergo Norrish type II elimination reactions under irradiation with UVA light in analogy to structurally related aromatic ketones. Moreover, efficient Norrish-Yang cyclization was observed from an adamantyl-substituted derivative. These results further demonstrate the ability of NHCs to influence the absorption properties and photochemical reactivity of carbonyl groups during a catalytic cycle.
Preparation method of vinylcyclohexane
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Paragraph 0028-0039, (2021/04/29)
The invention discloses a preparation method of vinylcyclohexane, and belongs to the technical field of organic synthesis. Cyclohexyl ketone is used as a raw material, and is firstly condensed with 2, 4, 6-triisopropylbenzenesulfonyl hydrazide to obtain 1-acetocyclohexane-2, 4, 6-triisopropylbenzenesulfonyl hydrazone; and reaction is carried out in the presence of an inorganic base and a non-nucleophilic strong base to obtain vinylcyclohexane. The method has the advantages of two-step reaction, simple route, high area selection and relatively easy product separation, and a certain amount of polymerization inhibitor needs to be added in the product distillation process to prevent polymerization in the distillation process.
A METHOD FOR PRODUCING VINYLCYCLOALKANES COMPOUNDS
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Paragraph 0047-0050, (2021/07/13)
The present invention relates to a method for producing vinylcycloalkanes compounds represented by the general formula (5) highly selectively and economically, which comprises hydrogenation and dehydration. Hydrogenation step: hydrogenating the compounds represented by the general formula (1) or/and (2) or/and (3) or/and (4) with hydrogen to prepare the corresponding primary or secondary alcohols in the presence of hydrogenation catalyst with min. 0.1 part by wight. Dehydration step: dehydrating the corresponding primary or secondary alcohols prepared by the above-mentioned hydrogenation step to prepare vinylcycloalkanes compounds represented by the general formula (5) in the presence of dehydration catalyst. R 1 -CH2-CH2-OH (1) Wherein R 1 of the general formula (1)~(4) is hydrocarbyl (hydrocarbon functional group) having aromatic rings. R 2 -CH=CH2(5) Wherein R 2 of the general formula (5) is cycloalkyl or cycloalkyl-substituted alkyl.
A Systems Approach to a One-Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode
Chakraborty, Biswarup,Kostenko, Arseni,Menezes, Prashanth W.,Driess, Matthias
supporting information, p. 11829 - 11834 (2020/08/19)
An unprecedented one-pot fully electrochemically driven Wittig olefination reaction system without employing a chemical reductant or sacrificial electrode material to regenerate triphenylphosphine (TPP) from triphenylphosphine oxide (TPPO) and base-free in situ formation of Wittig ylides, is reported. Starting from TPPO, the initial step of the phosphoryl P=O bond activation proceeds through alkylation with RX (R=Me, Et; X=OSO2CF3 (OTf)), affording the corresponding [Ph3POR]+X? salts which undergo efficient electroreduction to TPP in the presence of a substoichiometric amount of the Sc(OTf)3 Lewis acid on a Ag-electrode. Subsequent alkylation of TPP affords Ph3PR+ which enables a facile and efficient electrochemical in situ formation of the corresponding Wittig ylide under base-free condition and their direct use for the olefination of various carbonyl compounds. The mechanism and, in particular, the intriguing role of Sc3+ as mediator in the TPPO electroreduction been uncovered by density functional theory calculations.
Creation of Redox-Active PdSx Nanoparticles Inside the Defect Pores of MOF UiO-66 with Unique Semihydrogenation Catalytic Properties
Dong, Ming-Jie,Wang, Xuan,Wu, Chuan-De
, (2019/12/27)
Semihydrogenation of alkynes to produce alkenes is very important in the industry; however, over-hydrogenation heavily complicates the postprocesses, which are highly energy consuming and not environmentally friendly. One of the most efficient pathways to solve this challenging issue is to develop highly selective catalysts that could only hydrogenate alkynes and are inactive in hydrogenation of alkenes. This work presents herein an efficient catalyst, consisting of in situ created PdS0.53 nanoparticles as the redox-active sites inside the defect pores of metal–organic framework UiO-66, which demonstrates very high alkene selectivity (up to 99.5%) in semihydrogenation of easily over-hydrogenated terminal alkynes. In contrast to the traditional catalysts, strict control over the reaction time becomes the nonessential condition because the catalyst system is almost inactive in hydrogenation of alkenes. Therefore, this paradigm work provides a practically applicable pathway for the development of efficient catalysts with unique catalytic properties for selective semihydrogenation reactions.
Br?nsted Acid Catalyzed Peterson Olefinations
Britten, Thomas K.,McLaughlin, Mark G.
, p. 301 - 305 (2019/12/25)
A mild and facile Peterson olefination has been developed employing low catalyst loading of the Br?nsted acid HNTf2. The reactions are typically performed at room temperature, with the reaction tolerant to a range of useful functionalities. Furthermore, we have extended this methodology to the synthesis of enynes.
Transfer hydrogenation of alkynes into alkenes by ammonia borane over Pd-MOF catalysts
Bakuru, Vasudeva Rao,Samanta, Debabrata,Maji, Tapas Kumar,Kalidindi, Suresh Babu
supporting information, p. 5024 - 5028 (2020/05/08)
Ammonia borane with both hydridic and protic hydrogens in its structure acted as an efficient transfer hydrogenation agent for selective transformation of alkynes into alkenes in non-protic solvents. Catalytic synergy between the μ3-OH groups of the UiO-66(Hf) MOF and Pd active sites in Pd/UiO-66(Hf) furnished an elusive >98% styrene selectivity and full phenylacetylene conversion at room temperature. Such performance is not achievable by a Pd + UiO-66(Hf) physical mixture or by a commercial Pd/C catalyst.
An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- And Stereoselective Semihydrogenation of Internal and Terminal Alkynes
Bera, Jitendra K.,Choudhury, Joyanta,Das, Shubhajit,Dutta, Indranil,Pati, Swapan K.,Saha, Sayantani,Yadav, Suman
, p. 3212 - 3223 (2020/10/02)
The catalytic utility of [RuL1(CO)2I2] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L1), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBArF, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.
