620-23-5Relevant articles and documents
Silica-embedded tert-butyldimethylsilyltrifluoromethanesulfonate catalysts as new solid acid catalysts
Parvulescu,Gagea,Alifanti,Parvulescu,Parvulescu,Nae,Razus,Poncelet,Grange
, p. 319 - 323 (2001)
Silica-embedded tert-butyldimethylsilyltrifluoromethanesulfonate catalysts were synthesized by a sol-gel method in acidified CCl4, using hexadecyltrimethyl-ammonium bromide as a surfactant. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K; TG-DTA; 1H, 13C, and 29Si solid state MAS/NMR; XRD; XPS; Raman spectroscopy; and FTIR after adsorption of NH3. The characterization data indicated mesoporous solids in which most of the silyl-triflate derivative keeps its integrity. The catalytic tests performed with the methyl ester of 1-cyclopentenylacetic acid in various solvents showed that the reaction selectively leads to 3-methylbenzaldehyde and is sensitive to the solvent accepting ability.
The decomposition of methyl hemiacetals of benzaldehyde in aqueous solution: A study of the effect of aromatic substitution
Engell, Karen M.,McClelland, Robert A.,Sorensen, Poul E.
, p. 978 - 989 (1999)
The acid-base catalysed decomposition of hydrates and hemiacetals of carbonyl compounds are classical examples of reactions where (slow) proton transfer is coupled with heavy atom reorganization, i.e., C - O bond breaking and solvent reorganization. We have studied the influence of m- and p-substitution in the carbonyl electrophile on the kinetics of the acid and base catalysis of the decomposition of methyl hemiacetals of benzaldehyde. The experimental data are well described by three-dimensional More O'Ferrall - Jencks energy contour diagrams according to principles developed by Jencks (the BEMA HAPOTHLE). Thus, for acid catalysis, a Cordes cross-interaction coefficient pxy′ = ?ρ/?pKa = 0.15 indicates the coupled nature of the rate-limiting step in a class e mechanism, similar to conclusions reached from systematic substitution in the nucleophile. Our more extensive set of data for base catalysis permits a more rigorous analysis according to the BEMA HAPOTHLE. The data are consistent with a class n mechanism as also suggested earlier on the basis of substitution in the nucleophile. A slight upward curvature observed in the Hammett plots for the various catalysts is described by the direct correlation parameter py = ?ρ/?σ = -0.11. This second derivative demonstrates the concerted nature of the C - O bond cleavage and O-H formation in the transition state, which changes with changing substituent. A class n mechanism for base catalysis is also supported by the observation of a Cordes cross-interaction parameter pxy = ?ρ/?pKa = -?β/?σ = 0.03, which describes the experimentally observed decrease in Hammett ρ with increasing pKa of the catalyst. This change may be rationalized by the movement of a saddle point on a diagonal reaction coordinate in the energy contour diagram, as a resultant of shifts parallel and perpendicular to the coordinate, when the energy along one side of the diagram is changed. It is concluded that observed rate changes as a result of substitution in the electrophile are consistent with and present further confirmation of earlier suggested mechanisms of hemiacetal decomposition reactions.
A novel and active catalyst Ag/ZnO for oxidant-free dehydrogenation of alcohols
Hosseini-Sarvari, Mona,Ataee-Kachouei, Tahereh,Moeini, Fatemeh
, p. 98 - 105 (2015)
Nano Ag/ZnO catalysts were prepared by varying load of Ag on ZnO supports using a new and very simple method. The structure of nano Ag/ZnO has been confirmed by various techniques. The Ag/ZnO with 7.4 × 10-5 mol% of Ag has pore size distribution about 2.74 nm and this nano Ag/ZnO is found to be the best catalyst for oxidation of primary and secondary benzyl alcohols into corresponding aldehydes and ketones in oxidant-free at the atmospheric pressure. The influence of various parameters such as: solvent, base, temperature, time of reaction, etc. has been systematically studied on nano Ag/ZnO catalyst.
Selective Encapsulation and Unusual Stabilization of cis-Isomers by a Spherical Polyaromatic Cavity
Yuasa, Mana,Sumida, Ryuki,Tanaka, Yuya,Yoshizawa, Michito
supporting information, (2022/02/02)
To explore new cavity functions, we herein employed cis-trans stereoisomers with a N=N, C=C, or C=N unit as guest indicators for a polyaromatic capsule. Thanks to the rigid, spherical cavity with a diameter of ～1 nm, azobenzene and stilbene derivatives ar
Radical induced disproportionation of alcohols assisted by iodide under acidic conditions
Huang, Yang,Jiang, Haiwei,Li, Teng,Peng, Yang,Rong, Nianxin,Shi, Hexian,Yang, Weiran
supporting information, p. 8108 - 8115 (2021/10/29)
The disproportionation of alcohols without an additional reductant and oxidant to simultaneously form alkanes and aldehydes/ketones represents an atom-economical transformation. However, only limited methodologies have been reported, and they suffer from a narrow substrate scope or harsh reaction conditions. Herein, we report that alcohol disproportionation can proceed with high efficiency catalyzed by iodide under acidic conditions. This method exhibits high functional group tolerance including aryl alcohol derivatives with both electron-withdrawing and electron-donating groups, furan ring alcohol derivatives, allyl alcohol derivatives, and dihydric alcohols. Under the optimized reaction conditions, a 49% yield of 5-methyl furfural and a 49% yield of 2,5-diformylfuran were obtained simultaneously from 5-hydroxymethylfurfural. An initial mechanistic study suggested that the hydrogen transfer during this redox disproportionation occurred through the inter-transformation of HI and I2. Radical intermediates were involved during this reaction.
Gold Catalysts Can Generate Nitrone Intermediates from a Nitrosoarene/Alkene Mixture, Enabling Two Distinct Catalytic Reactions: A Nitroso-Activated Cycloheptatriene/Benzylidene Rearrangement
Cheng, Mu-Jeng,Kardile, Rahul Dadabhau,Kuo, Tung-Chun,Liu, Rai-Shung,More, Sayaji Arjun
supporting information, p. 5506 - 5511 (2021/07/31)
Gold-catalyzed reactions of cycloheptatrienes with nitrosoarenes yield nitrone derivatives efficiently. This reaction sequence enables us to develop gold-catalyzed aerobic oxidations of cycloheptatrienes to afford benzaldehyde derivatives using CuCl and nitrosoarenes as co-catalysts (10-30 mol %). Our density functional theory calculations support a novel nitroso-activated rearrangement, tropylium → benzylidene. With the same nitrosoarenes, we developed their gold-catalyzed [2 + 2 + 1]-annulations between nitrosobenzene and two enol ethers to yield 5-alkoxyisoxazolidines using 1,4-cyclohexadienes as hydrogen donors.
A Magnetically Recyclable Palladium-Catalyzed Formylation of Aryl Iodides with Formic Acid as CO Source: A Practical Access to Aromatic Aldehydes
You, Shengyong,Zhang, Rongli,Cai, Mingzhong
, p. 1962 - 1970 (2021/01/25)
A magnetically recyclable palladium-catalyzed formylation of aryl iodides under CO gas-free conditions has been developed by using a bidentate phosphine ligand-modified magnetic nanoparticles-anchored- palladium(II) complex [2P-Fe 3O 4@SiO 2-Pd(OAc) 2] as catalyst, yielding a wide variety of aromatic aldehydes in moderate to excellent yields. Here, formic acid was employed as both the CO source and the hydrogen donor with iodine and PPh 3as the activators. This immobilized palladium catalyst can be obtained via a simple preparative procedure and can be facilely recovered simply by using an external magnetic field, and reused at least 9 times without any apparent loss of catalytic activity.
Selective oxidation of alkenes to carbonyls under mild conditions
Huo, Jie,Xiong, Daokai,Xu, Jun,Yue, Xiaoguang,Zhang, Pengfei,Zhang, Yilan
supporting information, p. 5549 - 5555 (2021/08/16)
Herein, a practical and sustainable method for the synthesis of aldehydes, ketones, and carboxylic acids from an inexpensive olefinic feedstock is described. This transformation features very sustainable and mild conditions and utilizes commercially available and inexpensive tetrahydrofuran as the additive, molecular oxygen as the sole oxidant and water as the solvent. A wide range of substituted alkenes were found to be compatible, providing the corresponding carbonyl compounds in moderate-to-good yields. The control experiments demonstrated that a radical mechanism is responsible for the oxidation reaction.
Method for generating benzaldehyde by catalyzing alpha-monosubstituted styrene to be oxidized by N-hydroxyphthalimide
-
Paragraph 0057-0059, (2021/01/24)
The invention discloses a method for generating benzaldehyde by catalyzing alpha-mono-substituted styrene to be oxidized through N-hydroxyphthalimide. According to the method, N-hydroxyphthalimide isused as a catalyst, oxygen is used as an oxidizing agent, and an alpha mono-substituted styrene compound is oxidized in an organic solvent to obtain the benzaldehyde derivative. The method has the advantages of simple reaction operation, low cost, mild conditions, high yield, no heavy metal pollution and the like.
Hydroxyl radical-mediated oxidative cleavage of CC bonds and further esterification reaction by heterogeneous semiconductor photocatalysis
Hong, Mei,Jia, Rui,Miao, Hongyan,Ni, Bangqing,Niu, Tengfei,Wang, Hui
, p. 6591 - 6597 (2021/09/10)
A hydroxyl radical-mediated aerobic cleavage of alkenes and further sequence esterification reaction for the preparation of carbonyl compounds have been developed by using tubular carbon nitride (TCN) as a general heterogeneous photocatalyst under an oxygen atmosphere with visible light irradiation. This protocol has an excellent substrate scope and gives the desired aldehydes, ketones and esters in moderate to high yields. Importantly, this metal-free procedure employed photogenerated hydroxyl radicals in situ as green oxidation active species, avoiding the present additional initiators. The reaction could be carried out under solar light irradiation and was applicable to large-scale reactions. Furthermore, the recyclable TCN catalyst could be used several times without a significant loss of activities.
