582-25-2Relevant academic research and scientific papers
Significant effect of base on the improvement of selectivity in the hydrogenation of benzoic acid over NiZrB amorphous alloy supported on γ-Al2O3
Wen, Xin,Cao, Yingying,Qiao, Xianliang,Niu, Libo,Huo, Li,Bai, Guoyi
, p. 3281 - 3287 (2015)
This study presents a facile way to improve the selectivity for cyclohexanecarboxylic acid by adding a base in the hydrogenation of benzoic acid over a non-noble metal NiZrB amorphous alloy supported on γ-Al2O3. It is found that alkali metal carbonates exhibit an excellent selectivity improvement from 50.3% to a range of 93.5-95.7%, with the conversion of benzoic acid higher than 92.3%. Even a very small amount of K2CO3 (1 mol% benzoic acid) was efficient for improving the selectivity for cyclohexanecarboxylic acid. In addition, a lower reaction temperature was beneficial to the improvement of selectivity. Based on the results of temperature programmed desorption of NH3 and inductively coupled plasma analysis, the improvement of selectivity in the presence of a base was attributed to the neutralization of the acidic sites on the surface of the catalyst by the in situ generated potassium benzoate, inhibiting the hydrodeoxygenation of carbonyl and resulting in a high selectivity for cyclohexanecarboxylic acid.
Singlet oxygen production in the reaction of superoxide with organic peroxides
MacManus-Spencer, Laura A.,Edhlund, Betsy L.,McNeill, Kristopher
, p. 796 - 799 (2006)
A selective chemiluminescent probe for singlet oxygen has been employed to detect and quantify singlet oxygen in the reactions of superoxide with organic peroxides. The production of singlet oxygen has been quantified in the reaction of superoxide with benzoyl peroxide (BP). No singlet oxygen was detected in the reactions of superoxide with cumyl peroxide, tert-butyl peroxide, or tert-butyl hydroperoxide. On the basis of these results and on the temperature dependence of the reaction, we proposed a mechanism for singlet oxygen formation in the reaction of superoxide with BP.
An Anionic, Chelating C(sp3)/NHC ligand from the Combination of an N-heterobicyclic Carbene and Barbituric Heterocycle
Benaissa, Idir,Gajda, Katarzyna,Vendier, Laure,Lugan, No?l,Kajetanowicz, Anna,Grela, Karol,Michelet, Véronique,César, Vincent,Bastin, Stéphanie
, p. 3223 - 3234 (2021/09/30)
The coordination chemistry of the anionic NHC1-based on an imidazo[1,5-a]pyridin-3-ylidene (IPy) platform substituted at the C5 position by an anionic barbituric heterocycle was studied with d6(Ru(II), Mn(I)) and d8(Pd(II), Rh(I), Ir(I), Au(III)) transition-metal centers. While the anionic barbituric heterocycle is planar in the zwitterionic NHC precursor 1·H, NMR spectroscopic analyses supplemented by X-ray diffraction studies evidenced the chelating behavior of ligand 1-through the carbenic and the malonic carbon atoms in all of the complexes, resulting from a deformation of the lateral barbituric heterocycle. The complexes were obtained by reaction of the free carbene with the appropriate metal precursor, except for the Au(III) complex 10, which was obtained by oxidation of the antecedent gold(I) complex [AuCl(1)]?with PhICl2as an external oxidant. During the course of the process, the kinetic gold(I) intermediate 9 resulting from the oxidation of the malonic carbon of the barbituric moiety was isolated upon crystallization from the reaction mixture. The νCOstretching frequencies recorded for complex [Rh(1)(CO)2] (5) demonstrated the strong donating character of the malonate-C(sp3)/NHC ligand 1-. The ruthenium complex [Ru(1)Cl(p-cymene)] (11) was implemented as a precatalyst in the dehydrogenative synthesis of carboxylic acid derivatives from primary alcohols and exhibited high activities at low catalyst loadings (25-250 ppm) and a large tolerance toward functional groups.
Ruthenium-catalyzed ester reductions applied to pharmaceutical intermediates
Shaalan, Youssef,Boulton, Lee,Jamieson, Craig
supporting information, p. 2745 - 2751 (2020/11/30)
Ruthenium pincer complexes were synthesized and used for catalytic ester reductions under mild conditions (～5 bar of hydrogen). An experimental design approach was used to optimize the conditions for yield, purity, and robustness. Evidence for the catalytically active ruthenium dihydride species is presented. Observed intermediates and side products, as well as time-course data, were used to build mechanistic insight. The optimized procedure was further demonstrated through scaled-up reductions of two pharmaceutically relevant esters, both in batch and continuous flow.
A Diaminopropane Diolefin Ru(0) Complex Catalyzes Hydrogenation and Dehydrogenation Reactions
Casas, Fernando,Trincado, Monica,Rodriguez-Lugo, Rafael,Baneerje, Dipshikha,Grützmacher, Hansj?rg
, p. 5241 - 5251 (2019/11/16)
New ruthenium (0) complexes with a cooperative diolefin diaminopropane (DAP) or the dehydrogenated iminopropenamide ligand (IPA) were synthesized for comparison with their diaminoethane (DAE)/ diazadiene (DAD) ruthenium analogues. These DAP/IPA complexes are efficient catalysts in dehydrogenation reactions of alkaline aqueous methanol which proceeds under mild conditions (T=70 °C) and of higher alcohols, forming the corresponding carbonate and carboxylates, respectively. The scope of the reaction includes an example of a 1,2-diol as model for biomass derived alcohols. Their catalytic applications are extended to the atom-efficient dehydrogenative coupling of alcohols and amines to amides. The reaction proceeds without any additives and is applicable to the synthesis of formamides from methanol. Moreover, DAP/IPA complexes catalyze the hydrogenation of a series of esters, lactone, ketone, activated olefin, aldehyde and imine substrates. The diaminopropane Ru catalyst exhibits higher activity compared to the dehydrogenated β-ketiminate (IPA) and previously studied DAD/DAE based catalysts. We present studies on their stoichiometric reactivity with relevance to their possible catalytic mechanisms and the isolation and full characterization of key reaction intermediates.
Lanthanoid complexes supported by retro-Claisen condensation products of β-triketonates
Abad Galán, Laura,Sobolev, Alexandre N.,Zysman-Colman, Eli,Ogden, Mark I.,Massi, Massimiliano
supporting information, p. 17469 - 17478 (2019/01/03)
β-Triketonates have been recently used as chelating ligands for lanthanoid ions, presenting unique structures varying from polynuclear assemblies to polymers. In an effort to overcome low solubility of the complexes of tribenzoylmethane, four β-triketones with higher lipophilicity were synthesised. Complexation reactions were performed for each of these molecules using different alkaline bases in alcoholic media. X-ray diffraction studies suggested that the ligands were undergoing decomposition under the reaction conditions. This is proposed to be caused by in situ retro-Claisen condensation reactions, consistent with two examples that have been reported previously. The lability of the lanthanoid cations in the presence of a varying set of potential ligands gave rise to structures where one, two, or three of the molecules involved in the retro-Claisen condensation reaction were linked to the lanthanoid centres. These results, along with measurements of ligand decomposition in the presence of base alone, suggest the solvent used will modulate the impact of the retro-Claisen condensation in these complexes.
Mechanistic investigation of imine formation in ruthenium-catalyzed N-alkylation of amines with alcohols
Yu, Xiaojun,Li, Yaqiu,Fu, Haiyan,Zheng, Xueli,Chen, Hua,Li, Ruixiang
, (2018/02/09)
Imines are observed frequently in ruthenium-catalyzed N-alkylation of amines with alcohols. Herein, nitrogen–phosphine functionalized carbene ligands were developed and used in ruthenium-catalyzed N-alkylation to explore the mechanism of imine formation. The results showed that strongly electron-donating ligands were beneficial for imine formation and alcohol dehydrogenation to generate acid. In addition, with an increase of electron density of nitrogen atom in substituted amines, the yield of imines in N-alkylation was improved. At the same time, with electron-rich imines as substrates, the transfer hydrogenation of imines became difficult. It is suggested that strongly electron-donating ligands and substrates caused an increase of electron density on the ruthenium center, which resulted in the elimination of hydrogen atoms in active species [LRuH2] as hydrogen gas rather than transfer onto the imine coordinated with the ruthenium center.
Efficient Method for Aromatic-Aldehyde Oxidation by Cleavage of Their Hydrazones Catalysed by Trimethylsilanolate
Burglova, Kristyna,Okorochenkov, Sergei,Budesinsky, Milos,Hlavac, Jan
, p. 389 - 396 (2017/01/24)
The reactions of hydrazones, derived from various aromatic aldehydes bound to Rink resin and hydrazines, with trimethylsilanolate have been studied. In this process, the aldehydes were oxidized to the corresponding carboxylic acids. The reaction was also tested with success in solution, with various aromatic aldehydes easily being oxidized in one pot via hydrazone formation and trimethylsilanolate treatment. A mechanism for the hydrazone cleavage is proposed. The reaction may be used as an alternative method for aldehyde oxidation with the selectivity complementary to that of currently used reactions.
Facile and direct synthesis of symmetrical acid anhydrides using a newly prepared powerful and efficient mixed reagent
Rouhi-Saadabad, Hamed,Akhlaghinia, Batool
, p. 479 - 485 (2015/01/30)
An efficient mixed reagent for direct synthesis of symmetrical carboxylic anhydrides from carboxylic acids has been prepared. Carboxylic acids are converted to anhydrides using triphenylphosphine/ trichloroisocyanuric acid under mild reaction conditions at room temperature. Short reaction time, excellent yields of products, low cost, availability of reagents, simple experimental procedure, and easy work-up of the products are the main advantages of the presented method.
One-pot odourless synthesis of thioesters via in situ generation of thiobenzoic acids using benzoic anhydrides and thiourea
Abbasi, Mohammad,Khalifeh, Reza
, p. 1265 - 1273 (2015/08/18)
An efficient and odourless procedure for a one-pot synthesis of thioesters by the reaction of benzoic anhydrides, thiourea and various organic halides (primary, allylic, and benzylic) or structurally diverse, electron-deficient alkenes (ketones, esters, and nitriles) in the presence of Et3 N has been developed. In this method, thiobenzoic acids were in situ generated from the reaction of thiourea with benzoic anhydrides, which were subjected to conjugate addition with electron-deficient alkenes or a nucleophilic displacement reaction with alkyl halides.
