2473-03-2Relevant articles and documents
Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism
Wang, Yulei,Huang, Zhidao,Leng, Xuebing,Zhu, Huping,Liu, Guixia,Huang, Zheng
supporting information, p. 4417 - 4429 (2018/04/05)
The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex (BQ-NCOP)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the (BQ-NCOP)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C2D5OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has (BQ-NCOP)IrI(alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of (BQ-NCOP)IrIII(H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium isotope effect for the pre-equilibrium formation of (BQ-NCOP)IrIII(H)(OEt) from the catalyst resting state via ethanol dissociation. Regardless of the substrate, ethanol dehydrogenation is the slow segment of the catalytic cycle, while alkene hydrogenation occurs readily following the rate-determining step, that is, β-hydride elimination of (BQ-NCOP)Ir(H)(OEt) to form (BQ-NCOP)Ir(H)2 and acetaldehyde. The latter is effectively converted to innocent ethyl acetate under the catalytic conditions, thus avoiding the catalyst poisoning via iridium-mediated decarbonylation of acetaldehyde.
PROCESS FOR THE PREPARATION OF ORGANIC HALIDES
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Paragraph 00162, (2017/08/01)
The present invention provides a halo-de-carboxylation process for the preparation of organic chlorides, organic bromides and mixtures thereof, from their corresponding carboxylic acids, using a chlorinating agent selected from trichloroisocyanuric acid (TCCA), dichloroisocyanuric acid (DCCA), or combination thereof, and a brominating agent.
Exceptionally high decarboxylation rate of a primary aliphatic acyloxy radical determined by radical product yield analysis and quantitative 1H-CIDNP spectroscopy
Fraind, Alicia,Turncliff, Ryan,Fox, Teri,Sodano, Justin,Ryzhkov, Lev R.
scheme or table, p. 809 - 820 (2012/06/29)
Symmetrical (RCO2CO2R; R=XCH2CH 2) and asymmetrical (RCO2CO2R′; R=C 9H19CH2CH2, R′=CH3 or m-ClC6H4) primary diacyl peroxides were thermally decomposed under different conditions to analyze the decarboxylation rates of the thermally generated acyloxy radicals. Quantitative models of the geminate product yields, and qualitative and quantitative 1H-CIDNP spectroscopy were used to obtain the decarboxylation rate estimates. Results reported here suggest that, unlike short chain acyloxy radicals such as propanoyloxyl, long chain acyloxy radicals possess the highest decarboxylation rates of all known acyloxy radicals, estimated at (0.5-1.5)× 10 12s-1 between 80 and 140°C. Given the nature of the dissociative state of acyloxy radicals, such rates appear to be the result of destabilization of the former by the steric bulk of the long chain substituents. Additionally, the rate of this order of magnitude suggests a nearly concerted decarboxylation of primary diacyl peroxides. Copyright
Oxidation of monohydric and dihydric alcohols with CCl4 catalyzed by molybdenum compounds
Khusnutdinov,Shchadneva,Burangulova,Muslimov,Dzhemilev
, p. 1615 - 1621 (2007/10/03)
Mo(CO)6 catalyzed oxidation of alcohols and diols with tetrachloromethane. Primary oxidation products in reaction of alcohols with CCl4 are alkyl hypochlorites, and final products depending on the structure of initial alcohol are aldehydes (as acetals), ketones, chloroketones, and esters.
Intramolecular homolytic displacements. 30. Functional decarbonylative transformations of aldehydes via homolytically induced decomposition of unsaturated peroxyacetals
Degueil-Castaing, Marie,Moutet, Laurent,Maillard, Bernard
, p. 3961 - 3965 (2007/10/03)
Homolytically induced decompositions of unsaturated peroxyacetals, synthesized from aldehydes, gave alkoxyalkoxyl radicals that yielded alkyl radicals by rapid β-scission. The latter radicals could react with several types of "transfer agents" to smoothly bring about homolytic decarbonylative functional group transformations of aldehydes into halides, hydrocarbons, xanthates, alkanenitriles, 2-alkyl-3-chloromaleic anhydrides, 1-phenylalk-1-ynes, and ethyl 2-alkylpropenoates.
Functional transformation of aldehydes and ketones via homolytic induced decomposition of unsaturated peroxy acetals and peroxy ketals
Moutet,Bonafoux,Degueil-Castaing,Maillard
, p. 139 - 140 (2007/10/03)
Induced decomposition of unsaturated peroxy acetals prepared from trimethyl orthoformate, dodecanal or 2-methyl-undecanal and 2,3-dimethyl-2-hydroperoxybut-3-ene, in the presence of ethyl iodoacetate, CC14 or dodecanethiol, allowed respectively their iodo-, chloro- and hydro-decarbonylation with yields of over 70%; the same reaction applied to the monoperoxy ketal or diperoxy ketal of cyclohexanone in the presence of ethyl iodoacetate resulted in its functional transformation in methyl 6-iodohexanoate or 1,5-diiodopentane with respective yields of 65 and 40%.
Halide exchange: Preparation of alkyl chlorides
Peyrat, Jean-Francois,Figadere, Bruno,Cave, Andre
, p. 4563 - 4567 (2007/10/03)
Primary alkyl bromides can be quantitatively converted into the corresponding chlorides under very mild reaction conditions. The neutral conditions required for such bromide displacements allow the presence of other functions on the substrate.
Desulfurization with Nickel and Cobalt Boride: Scope, Selectivity, Stereochemistry, and Deuterium-Labeling Studies
Back, Thomas G.,Baron, Denise L.,Yang, Kexin
, p. 2407 - 2413 (2007/10/02)
A variety of organosulfur compounds containing alkylthio and arylthio groups underwent reductive desulfurization under notably mild conditions when treated with nickel boride, generated in situ from nickel chloride hexahydrate and sodium borohydride in methanol-THF (3:1).Phenyl, chloro, and ester groups are not reduced under these conditions, while iodo, bromo, nitrile, aldehyde, ketone, cyclopropane, and olefinic functions are reduced either completely or partially.Deuterium-labeling studies indicate that the hydrogen that is incorporated into the product originates from both the sodium borohydride and the protic solvent, suggesting the intermediacy of dihydrogen.The epimers 3α- and 3β-(phenylthio)cholestane afforded 3α- and 3β-deuteriocholestane, respectively, demonstrating that the reaction proceeds with retention of configuration.The method may thus be employed for the stereospecific preparation of deuterated products from organosulfur compounds.Arguments are presented in support of a tentative mechanism involving an oxidative addition-reductive elimination sequence via a nickel hydride intermediate.
HOMOLOGATION DES DERIVES HALOGENES
Yankep, Emmanuel,Charles, Georges
, p. 427 - 430 (2007/10/02)
The halide R-X is converted, in two steps, to its homologous R-CH2-X.
A CONVENIENT METHOD FOR THE TRANSFORMATION OF ALCOHOLS TO ALKYL CHLORIDES USING N,N-DIPHENYLCHLOROPHENYLMETHYLENIMINIUM CHLORIDE
Fujisawa, Tamotsu,Iida, Sachio,,Sato, Toshio
, p. 1173 - 1174 (2007/10/02)
N,N-Diphenylchlorophenylmethyleniminium chloride reacts smoothly with a variety of alcohols in the presence of triethylamine to afford the corresponding alkyl chlorides in high yields.Replacement of a hydroxyl group at an asymmetric carbon atom with chloride proceeds with complete inversion.
