60-12-8

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Dauben,Coad

, p. 2928 (1949)

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Nitrogen and sulfur co-doped cobalt carbon catalysts for ethylbenzene oxidation with synergistically enhanced performance

Chen, Sheng,Wu, Yujie,Jie, Shanshan,Au, Chak Tong,Liu, Zhigang

, p. 9462 - 9467 (2019)

Heteroatom doping has been demonstrated to be an effective strategy for improving the performance of catalysts. In this paper, cobalt carbon catalysts co-doped with nitrogen and sulfur (N and S) were synthesized through a hydrothermal method with chelate composites involving melamine, thioglycolic acid (C2H4O2S), and tetrahydrate cobalt acetate (Co(OAc)2·4H2O). In addition, the selective oxidation of ethylbenzene under solvent-free conditions with molecular oxygen was used as a probe reaction to evaluate the activity of the catalysts. The optimized catalyst shows an ethylbenzene conversion of 48% with an acetophenone selectivity of 85%. Furthermore, the catalysts were systematically characterized by techniques such as TEM, SEM, XRD, Raman, and XPS. The results reveal that the species of cobalt sulfides and synergistic effects between N and S has inserted a key influence on their catalytic performance.

Tetrahedral Sn-silsesquioxane: Synthesis, characterization and catalysis

Beletskiy, Evgeny V.,Shen, Zhongliang,Riofski, Mark V.,Hou, Xianliang,Gallagher, James R.,Miller, Jeffrey T.,Wu, Yuyang,Kung, Harold H.,Kung, Mayfair C.

, p. 15699 - 15701 (2014)

A tetrahedral stannasilsesquioxane complex was synthesized as a racemic mixture using Sn(OiPr)4 and silsesquioxanediol, and its structure was confirmed with X-ray crystallography, NMR, and EXAFS. The complex was a Lewis acid, and both anti and syn-binding with Lewis bases were possible with the formation of octahedral Sn complexes. It was also a Lewis acid catalyst active for epoxide ring opening and hydride transfer.

A study of factors affecting α-(N-carbamoyl)alkylcuprate chemistry

Dieter,Topping,Nice

, p. 2302 - 2311 (2001)

The effect of Cu(I) salt (i.e., CuCN, CuCN·2LiCl, CuI), cuprate reagent, sec-butyllithium quality, solvent, and temperature upon the chemical yields obtained in the reactions of α-(N-carbamoyl)alkylcuprates [i.e., N-Boc-protected α-aminoalkylcuprates] with (E)1-iodo-1-hexene, 5,5-dimethyl-2-cyclohexenone, methylvinyl ketone, crotonate esters, and an acid chloride has been examined. Cuprate conjugate addition and vinylation reactions can succeed with low-quality sec-butyllithium, presumably containing insoluble lithium hydride and lithium alkoxide impurities, although yields are significantly lower than those obtained with high-quality s-BuLi, α-(N-Carbamoyl)alkylcuprates prepared from high-quality sec-butyllithium are thermally stable for 2-3 h at room temperature and are equally effective when prepared from either insoluble CuCN or THF-soluble CuCN·2LiCl. Use of the latter reagent permits rapid cuprate formation at -78 °C, thereby avoiding the higher temperatures required for cuprate formation from THF-insoluble CuCN that are problematic with solutions containing thermally unstable α-lithiocarbamates.

Biocatalytic reaction and recycling by using CO2-induced organic-aqueous tunable solvents

Broering, James M.,Hill, Elizabeth M.,Hallett, Jason P.,Liotta, Charles L.,Eckert, Charles A.,Bommarius, Andreas S.

, p. 4670 - 4673 (2006)

(Chemical Equation Presented) Tamed OATS: A scheme that integrates homogeneous biocatalysis in organic-aqueous mixtures with CO2-induced separation has been developed. This method allows for simultaneous product recovery and recycling of the homogeneous biocatalyst for reuse.

Altman,Li

, p. 2493 (1976)

Mono- and binuclear complexes of iron(II) and iron(III) with an N 4O ligand: Synthesis, structures and catalytic properties in alkane oxidation

Li, Fei,Wang, Mei,Ma, Chengbing,Gao, Aiping,Chen, Hongbo,Sun, Licheng

, p. 2427 - 2434 (2006)

Three mononuclear iron complexes and one binuclear iron complex, [Fe(tpoen)Cl]·0.5(Fe2OCl6) (1), [Fe(tpoen)Cl]PF6 (2), Fe(tpoen)Cl3 (3) and [{Fe(tpoen)}2(-O)](ClO4)4 (4) (tpoen = N-(2-pyridylmethoxyethyl)-N,N-bis(2-pyridylmethyl)amine), were synthesized as functional models of non-heme iron oxygenases. Crystallographic studies revealed that the Fe(ii) center of 1 is in a pseudooctahedral environment with a pentadentate N4O ligand and a chloride ion trans to the oxygen atom. The Fe(iii) center of 3 is ligated by three nitrogen atoms of tpoen and three chloride ions in a facial configuration. Each Fe(iii) center of 4 is coordinated with four nitrogen atoms and an oxygen atom of tpoen with the Fe-O-Fe angle of 172.0(3) A. Complexes 2, 3 and 4 catalysed the oxidation of cyclohexane with H2O2 in the total TNs of 24-36 with A/K ratios of 1.9-2.4. Under the same conditions they also catalysed both the oxidation of ethylbenzene to benzylic alcohol and acetobenzene with good activity (30-47 TN) and low selectivity (A/K 0.7), and the oxidation of adamantane with moderate activity (15-18 TN) and low regioselectivity (3°/2° 3.0-3.2). With mCPBA as oxidant the catalytic activities of 2, 3 and 4 increased 1.8 to 2.3-fold for the oxidation of cyclohexane and ethylbenzene and 6.3 to 7.5-fold for the oxidation of adamantane. Drastic enhancement of the regioselectivity was observed in the oxidation of adamantane (3°/2° 18.5-30.3). The Royal Society of Chemistry 2006.

Scale-up biopolymer-chelated fabrication of cobalt nanoparticles encapsulated in N-enriched graphene shells for biofuel upgrade with formic acid

Zhou, Shenghui,Dai, Fanglin,Dang, Chao,Wang, Ming,Liu, Detao,Lu, Fachuang,Qi, Haisong

, p. 4732 - 4747 (2019)

Exploring both high-performance catalytic materials from non-edible lignocellulosic biomass and selective hydrodeoxygenation of bioderived molecules will enable value-added utilization of renewable feedstocks to replace rapidly diminishing fossil resources. Herein, we developed a scale-up and sustainable method to fabricate gram-quantities of highly dispersed cobalt nanocatalysts sheathed in multilayered N-doped graphene (Co@NG) by using a biomacromolecule carboxymethyl cellulose (CMC) as a raw material. The ionic gelation of CMC, urea and Co2+ ions leads to uniform dispersion and chelation of different species, consequently resulting in the formation of highly distributed Co nanoparticles (NPs) (10.91 nm) with N-enriched graphene shells in the solid-state thermolysis process. The usage of urea as a non-corrosive activation agent can introduce a porous belt-like nanostructure and abundant doped nitrogen. Among all the prepared catalysts in this work, the optimized Co@NG-6 with the largest specific surface area (627 m2 g-1), the most and strongest basic sites, and the highest proportion of pyridinic-N (37.6%) and mesopores exhibited excellent catalytic activity (99% yield of 2-methoxy-p-cresol) for base-free transfer hydrodeoxygenation (THD) of vanillin using bioderived formic acid (FA) as a H source at 160 °C for 6 h. The poisoning tests and electron paramagnetic resonance (EPR) spectra verified that the strong interaction between N atoms and encapsulated Co NPs provided synergistic effects, which were essential for the outstanding catalytic performance of Co@NG-6. The deuterium kinetic isotope effect study clearly demonstrated that the formation of Co-H-via β-hydride elimination and protonation was the rate-determining step, and protic N-H+ and hydridic Co-H- were considered to be active intermediate species in the THD reaction. Furthermore, Co@NG-6 was highly stable for recycling owing to the graphene shells preventing Co NPs from corrosion and aggregation.

Soft ruthenium and hard Br?nsted acid combined catalyst for efficient cleavage of allyloxy bonds. Application to protecting group chemistry

Tanaka, Shinji,Suzuki, Yusuke,Saburi, Hajime,Kitamura, Masato

, p. 6559 - 6568 (2015)

Abstract We show that a monocationic CpRu(II) complex of quinaldic acid (QAH) and a monocationic CpRu(IV)(π-allyl)QA complex catalyze efficient cleavage of the allyloxy bond in allyl ethers, allyl esters, allyl carbonates, and allyl carbamates in methanol without the need for additional nucleophiles. The only co-product is volatile allyl methyl ether, enhancing operational simplicity during isolation of the deprotected alcohols, acids, and amines. This clean and high-performance catalytic system should contribute to protecting group chemistry during the multistep synthesis of pharmaceutically important natural products. Full details of this system, including the mechanism, are reported.

Regiodivergent Reductive Opening of Epoxides by Catalytic Hydrogenation Promoted by a (Cyclopentadienone)iron Complex

De Vries, Johannes G.,Gandini, Tommaso,Gennari, Cesare,Jiao, Haijun,Pignataro, Luca,Stadler, Bernhard M.,Tadiello, Laura,Tin, Sergey

, p. 235 - 246 (2022/01/03)

The reductive opening of epoxides represents an attractive method for the synthesis of alcohols, but its potential application is limited by the use of stoichiometric amounts of metal hydride reducing agents (e.g., LiAlH4). For this reason, the corresponding homogeneous catalytic version with H2 is receiving increasing attention. However, investigation of this alternative has just begun, and several issues are still present, such as the use of noble metals/expensive ligands, high catalytic loading, and poor regioselectivity. Herein, we describe the use of a cheap and easy-To-handle (cyclopentadienone)iron complex (1a), previously developed by some of us, as a precatalyst for the reductive opening of epoxides with H2. While aryl epoxides smoothly reacted to afford linear alcohols, aliphatic epoxides turned out to be particularly challenging, requiring the presence of a Lewis acid cocatalyst. Remarkably, we found that it is possible to steer the regioselectivity with a careful choice of Lewis acid. A series of deuterium labeling and computational studies were run to investigate the reaction mechanism, which seems to involve more than a single pathway.

One-Pot Bioelectrocatalytic Conversion of Chemically Inert Hydrocarbons to Imines

Chen, Hui,Tang, Tianhua,Malapit, Christian A.,Lee, Yoo Seok,Prater, Matthew B.,Weliwatte, N. Samali,Minteer, Shelley D.

supporting information, p. 4047 - 4056 (2022/02/10)

Petroleum hydrocarbons are our major energy source and an important feedstock for the chemical industry. With the exception of combustion, the deep conversion of chemically inert hydrocarbons to more valuable chemicals is of considerable interest. However, two challenges hinder this conversion. One is the regioselective activation of inert carbon-hydrogen (C-H) bonds. The other is designing a pathway to realize this complicated conversion. In response to the two challenges, a multistep bioelectrocatalytic system was developed to realize the one-pot deep conversion from heptane to N-heptylhepan-1-imine under mild conditions. First, in this enzymatic cascade, a bioelectrocatalytic C-H bond oxyfunctionalization step based on alkane hydroxylase (alkB) was applied to regioselectively convert heptane to 1-heptanol. By integrating subsequent alcohol oxidation and bioelectrocatalytic reductive amination steps based on an engineered choline oxidase (AcCO6) and a reductive aminase (NfRedAm), the generated 1-heptanol was successfully converted to N-heptylhepan-1-imine. The electrochemical architecture provided sufficient electrons to drive the bioelectrocatalytic C-H bond oxyfunctionalization and reductive amination steps with neutral red (NR) as electron mediator. The highest concentration of N-heptylhepan-1-imine achieved was 0.67 mM with a Faradaic efficiency of 45% for C-H bond oxyfunctionalization and 70% for reductive amination. Hexane, octane, and ethylbenzene were also successfully converted to the corresponding imines. Via regioselective C-H bond oxyfunctionalization, intermediate oxidation, and reductive amination, the bioelectrocatalytic hydrocarbon deep conversion system successfully realized the challenging conversion from inert hydrocarbons to imines that would have been impossible by using organic synthesis methods and provided a new methodology for the comprehensive conversion and utilization of inert hydrocarbons.

Protein powder derived nitrogen-doped carbon supported atomically dispersed iron sites for selective oxidation of ethylbenzene

Cheng, Yujie,Gan, Tao,He, Qian,He, Xiaohui,Huang, Liyun,Ji, Hongbing,Shi, Shaolin,Sun, Qingdi,Wang, Pengbo,Zhang, Hao,Zhang, Xingcong,Zhang, Ying

supporting information, p. 11711 - 11715 (2021/09/06)

Atomically dispersed Fe species embedded in the nitrogen-containing carbon supports (Fe1/NC) are successfully synthesized using a ball milling approach, with commercial protein powder as the nitrogen source. The catalyst exhibits outstanding performance in the oxidation of aromatic compounds containing saturated C-H bonds into corresponding ketones under ambient conditions, which is superior to those of a nanoparticle catalyst (Fen/NC) and a metal-free catalyst (NC).