822-50-4Relevant academic research and scientific papers
INTRAMOLECULAR CYCLIZATIONS OF ORGANOMETALLIC COMPOUNDS IV. HETEROATOM INFLUENCE ON CYCLIZATIONS OF ORGANOLITHIUM COMPOUNDS
Smith, Michael J.,Wilson, Stanley E.
, p. 4615 - 4618 (1981)
Alkoxyl groups in alkenyllithiums can influence the stereochemistry of cyclization.The presence of n-butyllithium increases the stereoselectivity such that only one stereochemistry results; the presence of TMEDA negates the heteroatom's influence so that only the other stereochemistry results.Yields are 33percent to 44percent.
INTRAMOLECULAR CYCLIZATIONS OF ORGANOMETALLIC COMPOUNDS V. 6,6-BIS(DIETHYLALUMINUM)-1-HEXENES TO SUBSTITUTED CYCLOPENTANES.
Smith, Michael J.,Wilson, Stanley E.
, p. 5013 - 5016 (1982)
3-Substituted-hex-1-en-5-ynes were cyclized by treatment with diethylaluminum hydride; in hydrocarbon/ether solvent, trans-2-substituted-methylcyclopentane is produced, while in the absence of ether, the product is 2-substituted-methylenecyclopentane.Yields are 69percent to 76percent.
Insights into the Major Reaction Pathways of Vapor-Phase Hydrodeoxygenation of m-Cresol on a Pt/HBeta Catalyst
Sun, Qianqian,Chen, Guanyi,Wang, Hua,Liu, Xiao,Han, Jinyu,Ge, Qingfeng,Zhu, Xinli
, p. 551 - 561 (2016/02/20)
Conversion of m-cresol was studied on a Pt/HBeta catalyst at 225-350°C and ambient hydrogen pressure. At 250°C, the reaction proceeds through two major reaction pathways: (1) direct deoxygenation to toluene (DDO path); (2) hydrogenation of m-cresol to methylcyclohexanone and methylcyclohexanol on Pt, followed by fast dehydration on Br?nsted acid sites (BAS) to methylcyclohexene, which is either hydrogenated to methylcyclohexane on Pt or ring-contracted to dimethylcyclopentanes and ethylcyclopentane on BAS (HYD path). The initial hydrogenation is the rate-determining step of the HYD path as its rate is significantly lower than those of subsequent steps. The apparent activation energy of the DDO path is 49.7 kJ mol-1 but the activation energy is negative for the HYD path. Therefore, higher temperatures lead to the DDO path becoming the dominant path to toluene, whereas the HYD path, followed by fast equilibration to toluene, is less dominant, owing to the inhibition of the initial hydrogenation of m-cresol.
Catalytic activity of Mo oxide before and after alkali metal addition for methylcyclohexane and methylcyclopentane compounds
Al-Kandari,Mohamed,Al-Kharafi,Katrib
, p. 189 - 193 (2015/07/27)
Abstract Different catalytic reactions of methylcyclohexane MCH are performed depending on the nature of the catalytic active site (s) and experimental conditions. Ring contraction RC catalytic processes, producing dimethylcyclopenanes DMCP's of high octane numbers as compared to MCH are catalysed by acidic function of zeolites systems such as HY. Better activity, selectivity and stability concerning these RC reactions were obtained using Pt/HY catalyst. At higher reaction temperature, dehydrogenation of MCH to toluene and hydrocracking reactions are catalyzed by Pt. Comparable catalytic behavior is obtained using a bifunctional (metal-acid) MoO2-x(OH)y/TiO2 (MoTi) system. Different metallic character strength is observed following the suppression of the Br?nsted acid MoOH function(s) to MoO2-x(OA)y/TiO2 (A = Na, K, Rb) by the addition of small amount of alkali metal A. Rubidium addition seems to be the most performant in the dehydrogenation of MCH to toluene. The metallic functions in MoTi and modified AMoTi are not efficient for RO in MCP. In-situ characterization of the different oxidation states of Mo at different experimental conditions were conducted using in-situ XPS-UPS techniques.
Synthesis, reactivity, and catalytic application of a nickel pincer hydride complex
Breitenfeld, Jan,Scopelliti, Rosario,Hu, Xile
experimental part, p. 2128 - 2136 (2012/06/01)
The nickel(II) hydride complex [(MeN2N)Ni-H] (2) was synthesized by the reaction of [(MeN2N)Ni-OMe] (6) with Ph2SiH2 and was characterized by NMR and IR spectroscopy as well as X-ray crystallography. 2 was unstable in solution, and it decomposed via two reaction pathways. The first pathway was intramolecular N-H reductive elimination to give MeN2NH and nickel particles. The second pathway was intermolecular, with H2, nickel particles, and a five-coordinate Ni(II) complex [(MeN2N)2Ni] (8) as the products. 2 reacted with acetone and ethylene, forming [( MeN2N)Ni-OiPr] (9) and [(MeN 2N)Ni-Et] (10), respectively. 2 also reacted with alkyl halides, yielding nickel halide complexes and alkanes. The reduction of alkyl halides was rendered catalytically, using [(MeN2N)Ni-Cl] (1) as catalyst, NaOiPr or NaOMe as base, and Ph2SiH2 or Me(EtO)2SiH as the hydride source. The catalysis appears to operate via a radical mechanism.
Avoiding olefin isomerization during decyanation of alkylcyano α,ω-dienes: A deuterium labeling and structural study of mechanism
Rojas, Giovanni,Wagener, Kenneth B.
, p. 4962 - 4970 (2008/12/20)
(Chemical Equation Presented) A two-step synthetic pathway involving decyanation chemistry for the synthesis of pure alkyl α,ω-dienes in quantitative yields is presented. Prior methodologies for the preparation of such compounds required 6-9 steps, sometimes leading to product mixtures resulting from olefin isomerization chemistry. This isomerization chemistry has been eliminated. Deuteration labeling and structural mechanistic investigations were completed to decipher this chemistry. Deuterium labeling experiments reveal the precise nature of this radical decyanation chemistry, where an alcohol plays the role of hydrogen donor. The correct molecular design to avoid competing intramolecular cyclization, and the necessary reaction conditions to avoid olefin isomerization during the decyanation process are reported herein.
Study of Ir/WO3/ZrO2-SiO2 ring-opening catalysts: Part II. Reaction network, kinetic studies and structure-activity correlation
Lecarpentier, Sebastien,van Gestel, Jacob,Thomas, Karine,Gilson, Jean-Pierre,Houalla, Marwan
, p. 49 - 63 (2008/09/17)
The present paper is the second part of a systematic study of the influence of W and Ir loading on the activity of Ir/WO3/ZrO2-SiO2 catalysts for the ring-opening reaction of naphthenic molecules using methylcyclohexane (MCH) as a model compound. A series of Si-stabilized tungstated zirconias, WOx/ZrO2-SiO2, containing up to 3.5 atom W/nm2, was prepared. Ir-based catalysts containing up to 1.2 wt% were obtained by impregnation of these solids. Characterization of the metal dispersion and catalyst acidity was described in a previous article. The objective of the present study was to determine the best metal/acid balance for optimal performance of Ir/WOx/ZrO2-SiO2 catalysts in the ring-opening reaction of MCH. Monofunctional (acid WOx/ZrO2-SiO2 or metal Ir/ZrO2-SiO2) and bifunctional (Ir/WO3/ZrO2-SiO2) catalysts were examined. Based on the analysis of the yields and products distributions, a reaction network was proposed, and kinetic data (e.g., activation energies, initial rates) were calculated. Correlations between characterization results obtained earlier (e.g., acidity, dispersion) and catalytic performance are also reported. The monofunctional acid catalysts WOx/ZrO2-SiO2 showed a low selectivity for ring opening. The ring-contraction activity developed for W surface density above a threshold value of 1 atom W/nm2. This was attributed to the appearance and the development of a relatively strong Broensted acidity monitored by infrared measurements. MCH ring contraction and C5 naphthene ring opening occur according to a classic acid mechanism. For low conversions, the monofunctional metal catalysts Ir/ZrO2-SiO2 exhibited significant selectivity for ring opening that decreased with increasing conversion. Because of the lack of ring-contraction products, the observed activity was attributed to the direct ring opening of the MCH. Ring opening and cracking occur according to a dicarbene mechanism. The study of MCH conversion on Ir/WOx/ZrO2-SiO2 catalysts indicated that MCH ring contraction to alkylcyclopentanes occurs before ring opening. The best yields for ring opening were obtained with the 1.2% Ir/WOx/ZrO2 (1.5 atom of W/nm2). Further increases in W surface density led to a decrease in the indirect ring-opening yield, attributed to a decrease in Ir dispersion. For bifunctional metal/acid catalysts, analysis of the mechanism is less straightforward. The activation energy for C6 ring contraction and indirect C6 ring opening is a function of the metal/acid ratio. For high ratios, indirect ring opening occurs essentially over metallic sites. A decrease in the metal/acid ratio enhances the contribution of acid mechanism.
A novel reduction of polycarboxylic acids into their corresponding alkanes using n-butylsilane or diethylsilane as the reducing agent
Nimmagadda, Rama D.,McRae, Christopher
, p. 3505 - 3508 (2007/10/03)
A convenient one-pot reaction has been developed for the reduction of polycarboxylic acids on aliphatic and aromatic systems to their corresponding alkanes. The reduction utilises either diethylsilane or n-butylsilane as the reducing agent in the presence of the Lewis acid catalyst tris(pentafluorophenyl)borane.
Methylcyclohexane ring-contraction: A sensitive solid acidity and shape selectivity probe reaction
Mcvicker, Gary B.,Feeley, Owen C.,Ziemiak, John J.,Vaughan, David E. W.,Strohmaier, Karl C.,Kliewer, Wayne R.,Leta, Daniel P.
, p. 2222 - 2226 (2007/10/03)
In this paper we describe the utility of an acid-catalyzed isomerization reaction, specifically, ring-contraction of methylcyclohexane to an isomeric mixture of alkylcyclopentanes as a tool for characterizing the acidic properties of a wide range of platinum-loaded solid acids. Methylcyclohexane isomerization is particularly useful as a solid acidity probe reaction since it is a simple molecule containing one six-membered ring and a single methyl group substituent. As a solid acidity probe molecule methylcyclohexane has a number of advantages over cyclohexane. Ring-contraction of cyclohexane produces a single product, methlycyclopentane. Methylcyclohexane ring-contraction, in contrast, yields a richer and thus more informative product mixture including ethylcyclopentane, and five isomeric dimethylcyclopentanes. For the first time it will be shown that variations in the three primary descriptors of solid acids, acid site density, acid site strength, and shape selectivity, within a wide range of amorphous and crystalline solid acids can be simultaneously ranked using a single component probe reaction, namely, methylcyclohexane ring-contraction.
Isomerization of cycloheptane, cyclooctane, and cyclodecane catalyzed by sulfated zirconia - Comparison with open-chain alkanes
Satoh, Daishi,Matsuhashi, Hiromi,Nakamura, Hideo,Arata, Kazushi
, p. 4343 - 4349 (2007/10/03)
The skeletal isomerization of cycloalkanes with the number of carbons greater than six, cycloheptane, cyclooctane, cyclodecane, and cyclododecane, was performed over sulfated zirconia in liquid phase at 50°C. A main product of methylcyclohexane was formed from cycloheptane via a protonated cyclopropane intermediate, protonated [4.1.0]bicycloheptane, together with small amounts of trans-1,2-dimethylcyclopentane, as- and trans-1,3- dimethylcyclopentanes, 1,1-dimethylcyclopentane, and ethylcyclopentane. A major product from cyclooctane was ethylcyclohexane via a protonated cyclobutane intermediate, protonated [4.2.0]bicyclooctane, followed by cis-1,3- dimethylcyclohexane in addition to small amounts of trans-1,2-, -1,3-, -1,4-dimethylcyclohexanes, 1,1-dimethylcyclohexane, and methylcycloheptane. The detailed reaction-paths for cycloheptane and cyclooctane were shown after additional examinations in reactions of methylcyclohexane, ethylcyclopentane, ethylcyclohexane, and 1,2-dimethylcyclohexane. Cyclodecane was dehydrogenated into cis- or trans-decaline with the evolution of a dihydrogen. Cyclododecane was converted into lots of products, more than 30 species.
