121-69-7Relevant articles and documents
Fluoro-functionalized polymeric N-heterocyclic carbene-zinc complexes: Efficient catalyst for formylation and methylation of amines with CO2 as a C1-building block
Yang, Zhen-Zhen,Yu, Bo,Zhang, Hongye,Zhao, Yanfei,Ji, Guipeng,Liu, Zhimin
, p. 19613 - 19619 (2015)
A fluoro-functionalized polymeric N-heterocyclic carbene (NHC)-Zn complex (F-PNHC-Zn) was designed and synthesized by taking fluorous imidazolium salts as precursors through a two-step alkylation. The resultant F-PNHC-Zn was applied in catalyzing the formylation and methylation of amines using CO2 as a C1 building block in the presence of organosilane, which showed much higher activity than the corresponding non-fluorous PNHC-Zn under identical conditions. N-Methylanilines with both electron-withdrawing and electron-donating groups all could be converted to the corresponding formamides and methylamines in >90% conversion. Quantitative conversion of N-methylaniline was obtained even under very low CO2 pressure (0.05 MPa diluted by N2). Moreover, F-PNHC-Zn was highly stable and easily recyclable for these reactions. This journal is
Isolable CO2 Adducts of Polarized Alkenes: High Thermal Stability and Catalytic Activity for CO2 Chemical Transformation
Zhou, Hui,Zhang, Rui,Lu, Xiao-Bing
, p. 326 - 334 (2019)
Various CO2 adducts of tetra-hydropyrimidin-2-ylidene (THPE) derived from the commercially available 1, 5-diazabicyclo[4.3.0]non-5-ene (DBN) were firstly synthesized. X-ray single crystal analysis revealed the bent geometry of the binding CO2 having an O?C?O angle of 127.50～129.51° for THPE?CO2 adducts. In situ FTIR experiments demonstrated that THPE?CO2 adducts had unprecedented thermal stability in DMSO, even at 100 °C without decomposition. It was found that the THPE?CO2 adducts were highly active in catalyzing the carboxylative cyclization of CO2 with propargylic alcohols under mild conditions, significantly higher than the previously reported organocatalysts. Various internal and terminal functionalized propargylic alcohols were tolerated in these processes to afford the corresponding α-alkylidene cyclic carbonates in moderate to good yields with complete (Z)-stereoselectivity. Isotope labeling, in combination with in-situ FTIR and stoichiometric experiments, reveal that the catalytic reaction tends to proceed via the THPE?CO2-mediated basic ionic pair mechanism. (Figure presented.).
Phenonium ions from the addition of phenyl cations to alkenes. Photochemical synthesis of (rearranged) aminoalkylanilines from haloanilines in the presence of alkenes and amines
Guizzardi, Benedetta,Mella, Mariella,Fagnoni, Maurizio,Albini, Angelo
, p. 1067 - 1074 (2003)
β-Aminoalkylanilines are smoothly obtained by irradiation of 4-chloro- and 4-fluoroanilines (as well as the N,N-dimethyl derivatives) in the presence of alkenes (1-hexene, cyclohexene) and amines (butylamine, piperidine) in polar, protic solvents such as trifluoroethanol (yield 40-75%). The reaction involves photoheterolysis of the haloaniline, addition of the resulting phenyl cation to the alkene and trapping of the phenonium cation by amine. A fraction (up to ca. 20%) of aminoalkylanilines resulting from Wagner-Meerwein rearrangement of the phenonium cation is obtained in some cases. Reduction and direct trapping of the phenyl cation by the amine compete with the above three-component synthesis in a less stabilizing solvent such as acetonitrile, but not in CF3-CH2OH.
Photoinduced, ionic Meerwein arylation of olefins
Mella,Coppo,Guizzardi,Fagnoni,Freccero,Albini
, p. 6344 - 6352 (2001)
Irradiation of 4-chloroaniline or of its N,N-dimethyl derivative in polar solvents generates the corresponding triplet phenyl cations. These are trapped by alkenes yielding arylated products in medium to good yields. B3LYP calculations show that the triplet cation slides with negligible activation energy to a bonded adduct with ethylene, whereas it forms only a marginally stabilized CT complex with water (chosen as a representative σ nucleophile). The structure of the final products depends on the preferred path from the adduct cation with the alkene. In the case of aryl olefins, this deprotonates to stilbene derivatives, while, from 2,3-dimethyl-2-butene and allytrimethylsilane, allylanilines are obtained by elimination of an electrofugal group in γ. In the case of mono- and disubstituted alkenes the cation adds chloride rather than eliminating and β-chloroalkylanilines are obtained. The regio- and sterochemistry of the addition across the alkene are best understood with a phenonium ion structure for the adduct. The nucleophile entering in fi can be varied under conditions in which the adduct cation is trapped more efficiently than the starting phenyl cation. Thus, β-methoxyalkylanilines are formed when the irradiation is carried out in methanol. β-Iodoalkylanilines are obtained in acetonitrile containing iodide and unsubstituted alkylanilines in the presence of sodium borohydride. A case of intramolecular nucleophilic trapping is found with 4-pentenoic acid. The reaction is a wide-scope ionic analogue of the radicalic Meerwin arylation of olefins.
Ionization of Porous Hypercrosslinked Polymers for Catalyzing Room-Temperature CO2 Reduction via Formamides Synthesis
Ren, Qinggang,Chen, Yaju,Qiu, Yongjian,Tao, Leiming,Ji, Hongbing
, p. 2919 - 2927 (2021)
Porous materials with heterogeneous nature occupy a pivotal position in the chemical industry. This work described a facile pre- and post-synthetic approach to modify porous hypercrosslinked polymer with quaternary ammonium bromide, rendering it as efficient catalyst for CO2 conversion. The as-prepared porous ionic polymer (PiP@QA) displayed an improved specific surface area of 301 m2·g?1 with hierarchically porous structure, good selective adsorption of CO2, as well as high ion density. Accordingly, PiP@QA catalyst exhibited excellent catalytic performances for the solvent-free synthesis of various formamides from CO2, amines and phenylsilane under 35?°C and 0.5?MPa. We speculated that the superior catalytic efficiency and broad substrate scope of this catalyst could be resulted from the synergistic effect of flexible ionic sites with unique nanoporous channel that might increase the collision probability of reactants and active sites as well as enhance the diffusion of reactants and products during the reaction process. With the good reusability, PiP@QA was also available for the efficient conversion of simulated flue gas (15% CO2 in N2, v/v) into target formamides with quantitative selectivity at room temperature, which further highlighted its industrial application potential in chemical recycling the real-word CO2 to valuable products. Graphic Abstract: [Figure not available: see fulltext.].
Interaction of retinoic acid radical cation with lysozyme and antioxidants: Laser flash photolysis study in microemulsion
Li, Kun,Wang, Mei,Wang, Ting,Sun, Dongmei,Zhu, Rongrong,Sun, Xiaoyu,Wu, Xianzheng,Wang, Shi-Long
, p. 1064 - 1070 (2013)
All-trans retinoic acid (ATRA) plays essential roles in the normal biological processes and the treatment of cancer and skin diseases. Considering its photosensitive property, many studies have been focused on the photochemistry of ATRA. In this study, we investigated the transient phenomena in the laser flash photolysis (LFP) of ATRA in microemulsion to further understand the photochemistry of ATRA. Results show that 355 nm LFP of ATRA in both acidic and alkaline conditions leads to the generation of retinoic acid cation radicals (ATRA?+) via biphotonic processes. The employment of microemulsion system allows us to investigate the reaction of hydrophobic ATRA?+ with molecules of different polarity. Therefore, we studied the reaction activity of ATRA?+ to many hydrophobic and hydrophilic molecules. Results show that ATRA?+ can efficiently interact with lysozyme, tyrosine, tryptophan and many antioxidants, such as curcumin (Cur), vitamin C (VC) and gallic acid (GA). The apparent rate constants of these reactions were measured and compared. These findings suggest that ATRA?+ is a reactive transient product which may pose damage to lysozyme, and antioxidants, such as Cur, VC and GA, may inactivate ATRA?+ by efficient quenching reactions. 355 nm laser flash photolysis of all-trans retinoic acid (ATRA) in microemulsion leads to the formation of retinoic acid cation radicals (ATRA?+) via biphotonic processes. Deprotonated form of ATRA is more favorable for the formation of ATRA?+. ATRA?+ is proved to be reactive to lysozyme, tyrosine and tryptophan which is suggestive of its destructive effect on proteins. Meanwhile, some antioxidants, such as curcumin, gallic acid and vitamin C, can efficiently interact with ATRA?+, which indicates that it may competitively protect proteins from the attack of ATRA?+ by inactivating free radical.
Selective N-Methylation of N-Methylaniline with CO2 and H2 over TiO2-Supported PdZn Catalyst
Arai, Masahiko,Cheng, Haiyang,Lin, Weiwei,Wu, Qifan,Zhang, Chao,Zhao, Fengyu
, p. 3285 - 3296 (2020)
A series of Pd-ZnO/TiO2, Pd/TiO2, and Pd/ZnO catalysts were synthesized and investigated for N-methylation of N-methylaniline (MA) to N,N-dimethylaniline (DMA) with CO2 and H2. A high performance was observed with a Pd-ZnO/TiO2 catalyst, with 99.9% DMA selectivity at 94% MA conversion. By contrast, both Pd/TiO2 and Pd/ZnO were less active and/or selective. The catalytic performance of Pd-ZnO/TiO2 largely depended on reduction temperature and ZnO loading. The rates for MA conversion (rateMA) and DMA production (rateDMA) increased linearly with the amount of PdZn alloy formed. The reaction was likely to take place via intermediates of N-methylformanilide (MFA) and formate. Formate was produced through the reduction of CO2 with H2 as confirmed by in situ diffuse reflectance Fourier transform infrared spectroscopy and then added to MA producing MFA, and finally, MFA was subsequently adsorbed and hydrogenated to DMA. All these steps were promoted by the PdZn alloy. The hydrogenation of MFA to DMA was much faster than the N-methylation of MA to MFA; DMA was stable, so the selectivity to DMA was almost 100% over the Pd-ZnO/TiO2 catalyst.
Capillary-Bound Dense Micelle Brush Supports for Continuous Flow Catalysis
Cai, Jiandong,Cui, Yan,Lin, Geyu,Liu, Qiuwen,Manners, Ian,Qiu, Huibin,Sun, Yan
, p. 24637 - 24643 (2021)
Flow reactors are appealing alternatives to conventional batch reactors for heterogeneous catalysis. However, it remains a key challenge to firmly immobilize the catalysts in a facile and flexible manner and to simultaneously maintain a high catalytic efficiency and throughput. Herein, we introduce a dense cylindrical micelle brush support in glass capillary flow reactors through a living crystallization-driven self-assembly process initiated by pre-immobilized short micelle seeds. The active hairy corona of these micellar brushes allows the flexible decoration of a diverse array of nanocatalysts, either through a direct capture process or an in situ growth method. The resulting flow reactors reveal excellent catalytic efficiency for a broad range of frequently utilized transformations, including organic reductions, Suzuki couplings, photolytic degradations, and multistep cascade reactions, and the system was both recyclable and durable. Significantly, this approach is readily applicable to long capillaries, which enables the construction of flow reactors with remarkably higher throughput.
Absolute Estimates of PdII(n2-Arene) C-H Acidity
Christman, William E.,Morrow, Travis J.,Arulsamy, Navamoney,Hulley, Elliott B.
, p. 2706 - 2715 (2018)
Thermodynamic acidity is one of the most widely used quantities for characterizing proton transfer reactions. Measurement of these values for catalytically relevant species can be challenging, often requiring direct observation of equilibria. The C-H bonds of aromatic substrates are proposed to become substantially polarized during electrophilic activation, but quantifying the absolute acidity of the intermediate M(n 2-arene) complexes is highly challenging. Using a system that intercepts nascent protons at electrophilic PdII arene complexes, a combined experimental and computational study has demonstrated these C-H bonds to be far more acidic (pKaCH3CN = 3-6) than many "nonbasic" substrates and additives that are present in electrophilic C-H activation catalysis, and the catalytic roles of these species may need to be reassessed.
On the mechanism of the N,N-dimethyl amination of Grignard reagents: A kinetic study
Erdik, Ender,Uelhue, Selma Ates
, p. 671 - 676 (2007)
A direct kinetic study is reported for the electrophilic amination of substituted phenylmagnesium bromides with N,N-dimethyl O-(mesitylenesulfonyl) hydroxylamine in THF. Rate data, Hammett relationship, and activation entropy are consistent with a SN2 displacement involving the attack of carbanions to sp3N in the amination reagent (AR). Copyright
