A familiar ring: An efficient catalytic asymmetric hetero‐ene reaction of 1,2‐dicarbonyl compounds (including isatins, α‐ketoesters, and glyoxal derivatives) is described. The catalyst system derived from 1 can be used for a broad substrate scope and the corresponding products were obtained in good yield and excellent enantioselectivity. M.S.=molecular sieves.
Hydrogen can be used as an energy carrier for renewable energy to overcome the deficiency of its intrinsically intermittent supply. One of the most promising application of hydrogen energy is on‐board hydrogen fuel cells. However, the lack of a safe, efficient, convenient, and low‐cost storage and transportation method for hydrogen limits their application. The feasibility of mainstream hydrogen storage techniques for application in vehicles is briefly discussed in this Review. Formic acid (FA), which can reversibly be converted into hydrogen and carbon dioxide through catalysis, has significant potential for practical application. Historic developments and recent examples of homogeneous noble metal catalysts for FA dehydrogenation are covered, and the catalysts are classified based on their ligand types. The Review primarily focuses on the structure−function relationship between the ligands and their reactivity and aims to provide suggestions for designing new and efficient catalysts for H2 generation from FA.
A highly efficient chiral N,N'-dioxide-Mg(OTf)2 catalyst system has been developed for the asymmetric 1,3-dipolar cycloaddition between methyleneindolinones and N,N'-cyclic azomethine imines. The desired pyrazolidine products with contiguous quaternary-tertiary stereocenters were obtained in up to 99% yields with up to 99% ee and >19:1 dr under mild reaction conditions.
Formic acid (FA) is considered to be a potential hydrogen storage material. Homogeneous catalysts are desired, which decompose aqueous FA into H 2 and CO 2 without addition of organic additives as they can contaminate the generated gas mixture. We report a new series of Cp*Ir (Cp* = pentamethylcyclopentadienyl) catalysts featuring picolinamide-based ligands for efficient H 2 generation from FA solution. Among them in-situ generated catalyst from [Cp*Ir(H 2 O) 3 ]SO 4 and picolinohydroxamic acid (L3) achieved a high turnover frequency (TOF) of 90625 h À 1 at 80 °C in 0.9 M FA solution and a turnover number (TON) of 120520 at 80 °C in a recycle experiment. The substituent effect of amide N atom was discussed and a plausible mechanism was proposed based on the experimental results.
A diastereodivergent direct catalytic asymmetric inverse electron demand Diels−Alder reaction between ketenes and 3-alkylenyloxindoles was accomplished by using chiral N,N′dioxide/gadolinium complexes. By adjusting only the substituents of the ligand and retaining other catalysis conditions, both syn-and anti-indole-fused dihydropyranones bearing two vicinal stereogenic centers were obtained in high yields with excellent ee values. Thus, by changing the configuration of the chiral ligands, all stereoisomers could be obtained from the same set of starting materials.
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