Dioxygen activation by copper complexes is a valuable method to achieve oxidation reactions for sustainable chemistry. The development of a catalytic system requires regeneration of the CuI active redox state from CuII. This is usually achieved using extra reducers that can compete with the CuII(O2) oxidizing species, causing a loss of efficiency. An alternative would consist of using a photosensitizer to control the reduction process. Association of a RuII photosensitizing subunit with a CuII pre‐catalytic moiety assembled within a unique entity is shown to fulfill these requirements. In presence of a sacrificial electron donor and light, electron transfer occurs from the RuII center to CuII. In presence of dioxygen, this dyad proved to be efficient for sulfide, phosphine, and alkene catalytic oxygenation. Mechanistic investigations gave evidence about a predominant 3O2 activation pathway by the CuI moiety. 相似文献
A simple and practical procedure for the reduction of acetals to ethers is described. It is based on the use of a 1,1,3,3-tetramethyldisiloxane (TMDS)-Pd/C system in the presence of a Brønsted acid as the co-catalyst. The reaction occurs under mild conditions and ethers are obtained in high yields. 相似文献
A simple and convenient method for the chemoselective reduction of nitriles into aldehydes using a 1,1,3,3-tetramethyldisiloxane (TMDS)/triisopropoxyvanadium(V) oxide reducing system is described. Aromatic as well as aliphatic nitriles are reduced into the corresponding aldehydes in moderate to good yields. 相似文献
It is known that, given a vector-valued modular form of negative weight, its Fourier coefficients can be calculated based on the principal part of the form. In this paper we start with an arbitrary principal part and complete the Fourier expansion using the calculation. We show that the so-obtained function is a vector-valued modular integral of negative weight on the full modular group. Next, we construct the supplementary function associated to a vector-valued modular cusp form of positive weight. The constructions are inspired by the construction of Eichler integrals by Knopp. We conclude with a comparison of these forms and their integrals to vector-valued weak harmonic Maass forms. 相似文献
Summary Tetrachlorouranium complexes containing a Schiff base ligand, p-XC6H4NH=CHC6H4OH(L), derived from p-XC6H4NH2 and salicylaldehyde, have been prepared. Atris complex was obtained when X=NO2 andbis complexes for the other p-substituted Schiff bases when X=Cl, Br, OH and Me. 相似文献
The spectroscopic characterization (1H, 13C{1H} NMR, UV–Vis) and single-crystal X-ray diffraction (scXRD) analysis accomplished by inspection of the Hirshfeld surface of bis(3-thienoyl) disulfide (1) is described. The title compound 1 crystallizes in the monoclinic space group P21/n. The unit cell parameters are a?=?7.9959(3) Å, b?=?6.4348(3) Å, c?=?22.4924(9) Å, β?=?100.108(4)°, V?=?1139.32(8) Å3, Z?=?4, Rgt(F)?=?0.0278, wRref(F2)?=?0.0667. The packing of 1 is dominated by S?O and S?S interactions, giving a 2D layer structure parallel to (101). The X‐ray crystal structure analysis revealed the packing of 1 is dominated by S?O and S?S interactions, giving a 2D layer structure parallel to (101). The intermolecular interactions in 1 were analyzed using the Hirshfeld surface method including 2D fingerprint plots and enrichment ratios (E), which shows that the most favored intermolecular contacts are the O?H and C?S indicated by E values above 1.30. The interaction energies between molecular pairs revealed the importance of the weak O?H and C?S interactions in stabilizing the molecular structure of 1.
Graphic Abstract
Single crystal X-ray structure analysis, DFT calculations and Hirshfeld surface analysis to identify intermolecular interactions within the solid state structure of bis(3-thienoyl) disulfide (1).
Hyperpolarisation methods that premagnetise agents such as pyruvate are currently receiving significant attention because they produce sensitivity gains that allow disease tracking and interrogation of cellular metabolism by magnetic resonance. Here, we communicate how signal amplification by reversible exchange (SABRE) can provide strong 13C pyruvate signal enhancements in seconds through the formation of the novel polarisation transfer catalyst [Ir(H)2(η2‐pyruvate)(DMSO)(IMes)]. By harnessing SABRE, strong signals for [1‐13C]‐ and [2‐13C]pyruvate in addition to a long‐lived singlet state in the [1,2‐13C2] form are readily created; the latter can be observed five minutes after the initial hyperpolarisation step. We also demonstrate how this development may help with future studies of chemical reactivity. 相似文献
Facial selectivity during the π-coordination of pseudo-tetrahedral iridacycles by neutral (Cr(CO)(3)), monocationic (Cp*Ru(+)), and biscationic (Cp*Ir(2+)) metal centers was directly influenced by the coulombic imbalance in the coordination sphere of the chelated Ir center. We also showed by using theoretical calculations that the feasibility of the related metallacycles that displayed metallocenic planar chirality was dependent to the presence of an electron-donating group, such as NMe(2), which contributed to the overall stability of the complexes. When the π-bonded moiety was the strongly electron-withdrawing Cp*Ir(2+) group, the electron donation from NMe(2) resulted in major conformational changes, with a barrier to rotation of about 17?kcal mol(-1) for this group that became spectroscopically diastereotopic (high-field (1)H?NMR spectroscopy). This peculiar property is proposed as a means to introduce a new type of constitutional chirality at the nitrogen center: planar chirality at tertiary aromatic amines. 相似文献
A protocol is described for the reduction of carboxylic acids to primary alcohols using 1,1,3,3-tetramethyldisiloxane (TMDS) and a catalytic amount of Cu(OTf)2. Aliphatic as well as aromatic carboxylic acids are reduced in high selectivity and good yields. TMDS/Cu(OTf)2 has also been found to be an efficient catalytic reducing system for the preparation of symmetrical ethers from carbonyl compounds under mild conditions. 相似文献