1940-18-7Relevant articles and documents
Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
supporting information, p. 9925 - 9937 (2021/06/30)
A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
ETHERS AND ESTERS OF 1-SUBSTITUTED CYCLOALKANOLS FOR USE AS AROMA CHEMICALS
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, (2020/05/21)
The present invention relates to the use of an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use thereof for modifying the scent character of a fragranced composition; to an aroma chemical composition containing an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition. The invention further relates to specific ethers or esters of 1 -substituted cycloalkanols.
Inexpensive and rapid hydrogenation catalyst from CuSO4/CoCl2 — Chemoselective reduction of alkenes and alkynes in the presence of benzyl protecting groups
Ficker, Mario,Svenningsen, S?ren W.,Larribeau, Thomas,Christensen, J?rn B.
supporting information, p. 1125 - 1129 (2018/02/21)
The simple reduction of a number of alkenes and alkynes was performed with a typical reaction time of 20 min using a copper-cobalt catalytic system. The reduction did not cleave benzyl protecting groups which are usually vulnerable to catalytic hydrogenation reactions. The catalyst can be prepared in situ by reduction of the inexpensive precursor salts CuSO4 and CoCl2 with NaBH4. Sodium borohydride was also used as an easily handled hydrogen source for the catalytic reductions. No pressure, heating or inert atmosphere is required and purification/catalyst removal is achieved using extraction procedures, making this approach simple and efficient.
Palladium-Catalyzed C(sp3)?H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
St John-Campbell, Sahra,Ou, Alex K.,Bull, James A.
supporting information, p. 17838 - 17843 (2018/11/23)
C?H Functionalization of amines is a prominent challenge due to the strong complexation of amines to transition metal catalysts, and therefore typically requires derivatization at nitrogen with a directing group. Transient directing groups (TDGs) permit C?H functionalization in a single operation, without needing these additional steps for directing group installation and removal. Here we report a palladium catalyzed γ-C?H arylation of amines using catalytic amounts of alkyl acetals as transient activators (e.g. commercially available (2,2-dimethoxyethoxy)benzene). This simple additive enables arylation of amines with a wide range of aryl iodides. Key structural features of the novel TDG are examined, demonstrating an important role for the masked carbonyl and ether functionalities. Detailed kinetic (RPKA) and mechanistic investigations determine the order in all reagents, and identify cyclopalladation as the turnover limiting step. Finally, the discovery of an unprecedented off-cycle free-amine directed ?-cyclopalladation of the arylation product is reported.
Colloid and nanosized catalysts in organic synthesis: XI. Hydrogenation of alkynes catalyzed by nickel nanoparticles
Popov, Yu. V.,Mokhov,Nebykov
, p. 43 - 45 (2016/03/12)
The reaction of alkynes with hydrogen under atmospheric pressure in the presence of nickel nanoparticles as a catalyst led to the exhaustive hydrogenation of the triple bond.
Application of Pd Nanoparticles Supported on Mesoporous Hollow Silica Nanospheres for the Efficient and Selective Semihydrogenation of Alkynes
Verho, Oscar,Zheng, Haoquan,Gustafson, Karl P. J.,Nagendiran, Anuja,Zou, Xiaodong,B?ckvall, Jan-E.
, p. 773 - 778 (2016/03/05)
Herein, the preparation of a heterogeneous catalyst consisting of 1-2 nm sized Pd nanoparticles supported on amino-functionalized mesoporous hollow silica nanospheres and its use for the semihydrogenation of mono- And disubstituted alkynes is reported. By utilizing this Pd nanocatalyst together with the green poisoning agent DMSO, high yields of the desired alkenes could be achieved, while suppressing the degree of over-reduction to alkanes. To our delight, the Pd nanocatalyst displayed remarkable chemoselectivity towards the alkyne moiety, allowing the transformation to be carried out in the presence of other reducible functionalities, such as halogens, carbonyl, and nitro groups.
One-pot room-temperature conversion of cyclohexane to adipic acid by ozone and UV light
Hwang, Kuo Chu,Sagadevan, Arunachalam
, p. 1495 - 1498 (2015/02/19)
Nitric acid oxidation of cyclohexane accounts for ～95% of the worldwide adipic acid production and is also responsible for ～5 to 8% of the annual worldwide anthropogenic emission of the ozone-depleting greenhouse gas nitrous oxide (N2O). Here we report a N2O-free process for adipic acid synthesis.Treatment of neat cyclohexane, cyclohexanol, or cyclohexanone with ozone at room temperature and 1 atmosphere of pressure affords adipic acid as a solid precipitate. Addition of acidic water or exposure to ultraviolet (UV) light irradiation (or a combination of both) dramatically enhances the oxidative conversion of cyclohexane to adipic acid.
Selective activation of secondary C-H bonds by an iron catalyst: Insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
Cheng, Shi,Li, Jing,Yu, Xiaoxiao,Chen, Chuncheng,Ji, Hongwei,Ma, Wanhong,Zhao, Jincai
, p. 3267 - 3273 (2013/10/01)
In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′- dicarboxylic acid), which could activate the C-H bonds of cycloalkanes with high secondary (2°) C-H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C-H bonds, 1 always preferred to oxidise the 2° C-H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and >99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C-H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst.
Highly selective hydrogenation of multiple carbon-carbon bonds promoted by nickel(0) nanoparticles
Alonso, Francisco,Osante, I?aki,Yus, Miguel
, p. 93 - 102 (2007/10/03)
A new method for the highly stereoselective cis semihydrogenation of internal alkynes, semihydrogenation of terminal alkynes, reduction of dienes to alkenes, and reduction of alkynes and alkenes to alkanes is described based on in situ generated both Ni(0) nanoparticles and molecular hydrogen.
Development of a continuous-flow system for catalysis with palladium(0) particles
Solodenko, Wladimir,Wen, Hongliang,Leue, Stefanie,Stuhlmann, Friedrich,Sourkouni-Argirusi, Georgia,Jas, Gerhard,Schoenfeld, Hagen,Kunz, Ulrich,Kirschning, Andreas
, p. 3601 - 3610 (2007/10/03)
Heterogeneous catalysis for organic synthesis under continuous-flow conditions becomes possible by a new reactor-based approach. Continuous-flow reactors with a monolithic glass/polymer composite interior are loaded with palladium particles by ion exchange followed by reduction. When incorporated into a continuous-flow setup (PASSflow) this reactor allows the transfer-hydrogenation of alkenes, alkynes, nitro-substituted aromatic compounds and benzyl ethers in the flow-through mode. In addition, the activity of the catalysts is well suited to achieve Suzuki, Sonogashira and Heck cross-coupling reactions in the absence of phosphanes or any other ligands, resulting in a greatly simplified purification. As an extension to this concept a bifunctional support was prepared inside the reactor consisting of Pd particles and an ion-exchange group (hydroxide form). In the Suzuki-Miyaura reaction the reactor serves as a base for immobilisation and activation of the boronic acid as boronate and as a catalyst for promoting the C-C coupling reaction under continuous-flow conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
