ACS Organic & Inorganic Au最新文献

Organic compounds bearing both silyl and boryl groups are important building blocks in organic synthesis because of the adequate reactivity of the silyl and boryl groups and high stereospecificity in their derivatization reactions. The difference in reactivity between the silyl and boryl groups enables stepwise derivatization of these groups to afford complex molecules. Here, we report the copper(I)-catalyzed silaboration of terminal allenes to produce multisubstituted allylic boronates embedded with an alkenyl silane structure. The reaction can proceed with a variety of allenes and silylboranes. Furthermore, the silyl and boryl groups were successfully converted into other functional groups, while retaining the stereochemistry of the alkene moiety.

Organometallic catalysis is a powerful strategy in chemical synthesis, especially with the cheap and low toxic metals based on green chemistry principle. Thus, the selection of the metal is particularly important to plan relevant and applicable processes. The group VB metals have been the subject of exciting and significant advances in both organic and inorganic synthesis. In this Review, we have summarized some reports from recent decades, which are about the development of group VB metals utilized in various types of reactions, such as oxidation, reduction, alkylation, dealkylation, polymerization, aromatization, protein synthesis, and practical water splitting.

Throughout the last 15 years, there has been increased research interest in the use of light promoting organic transformations. [2 + 2] Cycloadditions are usually performed photochemically; however, literature precedent on the reaction between olefins and maleimides is limited to a handful of literature examples, focusing mainly on N-aliphatic maleimides or using metal catalysts for visible-light driven reactions of N-aromatic maleimides. Herein, we identify the differences in reactivity between N-alkyl and N-aryl maleimides. For our optimized protocols, in the case of N-alkyl maleimides, the reaction with alkenes proceeds under 370 nm irradiation in the absence of an external photocatalyst, leading to products in high yields. In the case of N-aryl maleimides, the reaction with olefins requires thioxanthone as the photosensitizer under 440 nm irradiation.

We report the facile synthesis of a rare niobium(V) imido NHC complex with a dianionic OCO-pincer benzimidazolylidene ligand (L¹) with the general formula [NbL¹(N^tBu)PyCl] 1-Py. We achieved this by in situ deprotonation of the corresponding azolium salt [H₃L¹][Cl] and subsequent reaction with [Nb(N^tBu)Py₂Cl₃]. The pyridine ligand in 1-Py can be removed by the addition of B(C₆F₅)₃ as a strong Lewis acid leading to the formation of the pyridine-free complex 1. In contrast to similar vanadium(V) complexes, complex 1-Py was found to be a good precursor for various salt metathesis reactions, yielding a series of chalcogenido and pnictogenido complexes with the general formula [NbL¹(N^tBu)Py(EMes)] (E = O (2), S (3), NH (4), and PH (5)). Furthermore, complex 1-Py can be converted to alkyl complex (6) with 1 equiv of neosilyl lithium as a transmetallation agent. Addition of a second equivalent yields a new trianionic supporting ligand on the niobium center (7) in which the benzimidazolylidene ligand is alkylated at the former carbene carbon atom. The latter is an interesting chemically “noninnocent” feature of the benzimidazolylidene ligand potentially useful in catalysis and atom transfer reactions. Addition of mesityl lithium to 1-Py gives the pyridine-free aryl complex 8, which is stable toward “overarylation” by an additional equivalent of mesityl lithium. Electrochemical investigation revealed that complexes 1-Py and 1 are inert toward reduction in dichloromethane but show two irreversible reduction processes in tetrahydrofuran as a solvent. However, using standard reduction agents, e.g., KC₈, K-mirror, and Na/Napht, no reduced products could be isolated. All complexes have been thoroughly studied by various techniques, including ¹H-, ¹³C{¹H}-, and ¹H-¹⁵N HMBC NMR spectroscopy, IR spectroscopy, and X-ray diffraction analysis.

High-quality density functional theory calculations underscore a nearly 6 eV range for the ionization potentials (IPs) of neutral, low-valent carbon compounds, including carbenes, ylides, and zero-valent carbon compounds (carbones) such as carbodiphosphoranes (CDPs) and carbodicarbenes. Thus, adiabatic IPs as low as 5.5 ± 0.1 eV are predicted for CDPs, which are about 0.7–1.2 eV lower than those of simple phosphorus and sulfur ylides. In contrast, the corresponding values for N-heterocyclic carbenes are about 8.0 eV while those for simple singlet carbenes such as dichlorocarbene and difluorocarbene range from about 9.0 eV to well over 11.0 eV.

Anilines and substituted anilines are used on the multi-ton scale for producing polymers, pharmaceuticals, dyes, and other important compounds. Typically, these anilines are produced from their corresponding nitrobenzene precursors by reaction with hydrogen at high temperatures. However, this route suffers from a number of drawbacks, including the requirement to handle hydrogen gas, rather harsh reaction conditions that lead to a lack of selectivity and/or toleration of certain functional groups, and questionable environmental sustainability. In light of this, routes to the reduction of nitrobenzenes to their aniline derivatives that operate at room temperature, in aqueous solvent, and without the requirement to use harsh process conditions, hydrogen gas, or sacrificial reagents could be of tremendous benefit. Herein, we report on a highly selective electrocatalytic route for the reduction of nitrobenzenes to their corresponding anilines that works in aqueous solution at room temperature and which does not require the use of hydrogen gas or sacrificial reagents. The method uses a polyoxometalate redox mediator, which reversibly accepts electrons from the cathode and reacts with the nitrobenzenes in solution to reduce them to the corresponding anilines. A variety of substituted nitroarenes are explored as substrates, including those with potentially competing reducible groups and substrates that are difficult to reduce selectively by other means. In all cases, the selectivity for the redox-mediated route is higher than that for the direct reduction of the nitroarene substrates at the electrode, suggesting that redox-mediated electrochemical nitroarene reduction is a promising avenue for the more sustainable synthesis of substituted anilines.

Dissipative systems are based on the supply of energy to a system by fuel pulses and dissipation of this energy through the fuel decomposition, resulting in repetition of a given physical or biological function. Such out of equilibrium processes are at the heart of all living organisms, and in the past decade, researchers have attempted to transpose these principles to purely synthetic systems. However, upon fuel decomposition, the resulting waste generated tends to accumulate in the system, rapidly inhibiting the machinery after a few cycles of fuel pulses. In order to solve this issue, trichloroacetic acid has appeared as a fuel of choice to reversibly change the acidity of a system, liberating volatile chloroform and CO₂ upon fuel decomposition. In this Perspective, we present the advantages of this fuel and successful applications ranging from conformational switches to rotary motors to temporal control over crystallization or smart materials.

This work demonstrates a strategy to fine-tune the efficiency of a photoredox water splitting Ni(II) tris-pyridinethiolate catalyst through heteroleptic ligand design using computational investigation of the catalytic mechanism. Density functional theory (DFT) calculations, supported by topology analyses using quantum theory of atoms in molecules (QTAIM), show that the introduction of electron donating (ED) −CH₃ and electron withdrawing (EW) −CF₃ groups on the thiopyridyl (PyS^–) ligands of the same complex can tune the pK_a and E⁰, simultaneously. Computational modeling of two heteroleptic nickel(II) tris-pyridinethiolate complexes with 2:1 and 1:2 ED and EW −CH₃ and −CF₃ group containing PyS^– ligands, respectively, suggests that the ideal combination of EW to ED groups is 2:1. This work also outlines the possibility of formation of a large number of isomers after the protonation of one of the pyridyl N atoms and suggests that to acquire unambiguous computational results it is necessary to carefully account for all possible geometric isomers.