Low-temperature dehalogenation of benzyl halides with atomic magnesium in the3P state

Low-temperature reactions of benzyl halides with magnesium in the³P state proceed according to the radical mechanism accompanied by abstraction of the halogen atom by the biradical magnesium atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 147–151, January, 1999.     

Homogeneous Light‐Driven Catalytic Direct Carboxylation with CO2

Carbon dioxide is a ubiquitous and inexpensive one‐carbon source for chemical synthesis, and the efficient incorporation of CO₂ into organic molecules is of widespread research interest both for economic and ecological reasons. The methodologies to employ carbon dioxide as a single‐carbon unit to construct molecules relevant for agrochemical and pharmaceutical research include many elegant approaches, including asymmetric transformations. Even though remarkable achievements have been made in the field of light‐driven catalysis, especially photoredox catalysis, homogeneous light‐driven catalytic carboxylation by employing CO₂ as the key reagent has only become a subject of increasing attention in recent years. Therefore, this concise review will discuss the latest advances in this research area.     

Effective heterogeneous palladium catalysis of the reactions of organoboron compounds with aryl halides

Reactions of [Ph₄B]Na and ArB(OH)₂ with aryl halides are effectively catalyzed by heterogeneous palladium catalysts (PdCl₂C, Pd(0)/C, and palladium black) to give cross-coupling products in high yields. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1399–1401, July, 1997.     

Electrocatalytic Carbon Dioxide Reduction by Using Cationic Pentamethylcyclopentadienyl–Iridium Complexes with Unsymmetrically Substituted Bipyridine Ligands

Eight [Ir(bpy)Cp*Cl]⁺‐type complexes (bpy= bipyridine, Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) containing differently substituted bipyridine ligands were synthesized and characterized. Cyclic voltammetry (CV) of the complexes in Ar‐saturated acetonitrile solutions showed that the redox behavior of the complexes could be fine tuned by the electronic properties of the substituted bipyridine ligands. Further CV in CO₂‐saturated MeCN/H₂O (9:1, v/v) solutions showed catalytic currents for CO₂ reduction. In controlled potential electrolysis experiments (MeCN/MeOH (1:1, v/v), E_app=?1.80 V vs Ag/AgCl), all of the complexes showed moderate activity in the electrocatalytic reduction of CO₂ with good stability over at least 15 hours. This electrocatalytic process was selective toward formic acid, with only traces of dihydrogen or carbon monoxide and occasionally formaldehyde as byproducts. However, the turnover frequencies and current efficiencies were quite low. No direct correlation between the redox potentials of the complexes and their catalytic activity was observed.     

二氧化碳作为羧化试剂用于羧酸及其衍生物的合成(英文)

二氧化碳是储量丰富、廉价易得且可再生的C1资源,将其催化转化成高附加值精细化学品的研究已经引起了人们的广泛关注.目前,虽然二氧化碳用作初始原料的反应已经工业化的很少,但过去几十年中仍有二十多个具有实际应用前景的二氧化碳参与的新反应被发现,其中以二氧化碳作为羧化试剂合成各种羧酸及其衍生物的反应为突出代表.本文综述了过渡金属催化合成羧酸及其衍生物的二氧化碳与多种碳亲核试剂、碳氢键以及碳碳多重键化合物的反应,并总结了无过渡金属参与或有机小分子催化条件下将二氧化碳转化成羧酸及其衍生物的反应.     

Intermediates of the PTC carbonylation of benzyl halides by cobalt carbonyls, II

The structures of intermediates in the PTC carbonylation of two fluorinated benzyl halide substrates were studied. X-ray crystal and molecular structure of 2- and 3-fluorobenzylcobalt tricarbonyl triphenylphosphine derivatives was determined. The supposed influence of structural parameters on the reactivity is discussed.     

Palladium-catalyzed cascade reactions of benzyl halides with N-allyl-N-(2-butenyl)-p-toluenesulfonamide

Reaction of benzyl halides with N-allyl-N-(2-butenyl)-p-toluenesulfonamide 1 in the presence of a palladium catalyst afforded dihydropyrroles 3 in moderate to excellent yields. It is proposed that the cyclic products were formed via a palladium-catalyzed cascade cyclization-coupling process.     

The First Catalytic Synthesis of an Acrylate from CO2 and an Alkene—A Rational Approach

For more than three decades the catalytic synthesis of acrylates from the cheap and abundantly available C₁ building block carbon dioxide and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Herein, we describe a homogeneous catalyst based on nickel that permits the catalytic synthesis of the industrially highly relevant acrylate sodium acrylate from CO₂, ethylene, and a base, as demonstrated, at this stage, by a turnover number of greater than 10 with respect to the metal.     

Electrochemically Activated Reaction of Benzoyl Halides with Carbon Dioxide

The electrochemical activation and carboxylation of benzoyl halides (benzoyl bromide, chloride, and fluoride) were studied. It was found that the yield of phenylglyoxylic acid increases from zero to 88% in the transition from benzoyl fluoride to the chloride and bromide. The effect of the nature of the halogen atom in the benzoyl halide and also the nature of the supporting electrolyte and the electrode material on the electrochemical reduction and carboxylation of benzoyl halides was studied.     

Electrocatalytic reduction of organic halides with cobalt bipyridine complexes

The electrocatalytic reduction of organic halides by the [Nibpy]⁺complexes coordinationally unsaturated with bpy (at potentials of the first wave) and by the coordinationally saturated [Nibpy₂]^–complexes (at potentials of the second wave) was observed. The apparent rate constant of the process decreased with an increase in the difference of the reduction potentials of the substrate and catalyst in a large range of the driving force of the process.     

Experimental and theoretical investigations on the catalytic hydrosilylation of carbon dioxide with ruthenium nitrile complexes

Ruthenium complexes, mer-[RuX(3)(MeCN)(3)] and cis/trans-[RuX(2)(MeCN)(4)] with X=Br, Cl, were investigated as precatalysts in homogeneously catalyzed hydrosilylation of CO(2). The oxidation state of ruthenium and nature of the halide in the precatalysts were found to influence the catalytic activity in the conversion of Me(2)PhSiH to the formoxysilane Me(2)PhSiOCHO, with Ru(III) having chloride ligands being most active. Monitoring the reactions by in-situ IR spectroscopy in MeCN as the solvent indicates an interaction of the precatalyst with the silane prior to activation of CO(2). In the absence of CO(2), hydrosilylation of the MeCN solvent occurs. Catalytic activity in CO(2) hydrosilylation is enhanced by Me(2)PhSiCl, generated during reduction of Ru(III) in mer-[RuX(3)(MeCN)(3)] to Ru(II) or, when added as promoter to Ru(II) precatalysts. The reaction mechanism for the catalytic cycle has been calculated by DFT methods for the reaction of Me(3)SiH. The key steps are: Transfer of the Me(3)Si moiety to a coordinated halide ligand, resulting in an L(n)RuH(XSiMe(3)) intermediate --> CO(2) coordination --> Me(3)Si transfer to CO(2) --> reductive elimination of formoxysilane product. This reaction sequence is more favorable energetically for chloride complexes than for the analogous bromide complexes, which accounts for their differences in catalytic activity. Calculations also explain the rate increase observed experimentally in the presence of Me(2)PhSiCl. A parallel reaction pathway leads to (Me(3)Si)(2)O as a minor byproduct which arises from the condensation of two initially formed Me(3)SiOH molecules.     

Palladium‐Catalyzed Carbonylation Reactions of Aryl Halides and Related Compounds

A CO group richer : (Hetero)arenes are vital intermediates in the manufacture of agrochemicals, dyes, pharmaceuticals, and other industrial products. In the past decades transition‐metal‐catalyzed coupling reactions of aryl halides with all types of nucleophiles have been developed. This Review summarizes recent work in the area of palladium‐catalyzed carbonylation reactions of aryl halides and related compounds (see scheme).

     

Efficient Electrocarboxylation of p-Methylpropiophenone in the Presence of Carbon Dioxide

In the one compartment electrochemical cell 2‐hydroxy‐2‐p‐tolyl‐butyric acid methyl ester was electrosynthesized by electrochemical carboxylation of p‐methylpropiophenone in the presence of carbon dioxide. Under galvanostatic conditions, the electrocarboxylation was influenced by supporting electrolytes, cathode materials, the current density, passed charge and temperatures. Application scope of the eletrocarboxylation system was then examined, and an excellent yield of 97% was obtained when the electrolysis was carried out in DMF‐0.1 mol·L^?1 TEABr solution using cheap and environmentally benign nickel as the cathode under a controlled current density of 5.0 mA·cm^?2 until 2.8 F·mol^?1 charge passed through the cell at ?10°C. The electrochemical behavior of p‐methoxylacetophenone has been studied on the glassy carbon electrode by cyclic voltammetry and the probable mechanism was proposed accordingly.