RESUMEN
Transition metal-catalyzed organic electrochemistry is a rapidly growing research area owing in part to the ability of metal catalysts to alter the selectivity of a given transformation. This conversion mainly focuses on transition metal-catalyzed anodic oxidation and cathodic reduction and great progress has been achieved in both areas. Typically, only one of the half-cell reactions is involved in the organic reaction while a sacrificial reaction occurs at the counter electrode, which is inherently wasteful since one electrode is not being used productively. Recently, transition metal-catalyzed paired electrolysis that makes use of both anodic oxidation and cathodic reduction has attracted much attention. This perspective highlights the recent progress of each type of electrochemical reaction and relatively focuses on the transition metal-catalyzed paired electrolysis, showcasing that electrochemical reactions involving transition metal catalysis have advantages over conventional reactions in terms of controlling the reaction activity and selectivity and figuring out that transition metal-catalyzed paired electrolysis is an important direction of organic electrochemistry in the future and offers numerous opportunities for new and improved organic reaction methods.
RESUMEN
An electrochemical asymmetric coupling of secondary acyclic amines with ketones via a Shono-type oxidation has been described, affording the corresponding amino acid derivatives with good to excellent diastereoselectivity and enantioselectivity. The addition of an N-oxyl radical as a redox mediator could selectively oxidize the substrate rather than the product, although their oxidation potential difference is subtle (about 13 mV). This electrochemical transformation proceeds in the absence of stoichiometric additives, including metals, oxidants, and electrolytes, which gives it good functional group compatibility. Mechanistic studies suggest that proton-mediated racemization of the product is prevented by the reduction of protons at the cathode.
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A novel strategy for asymmetric Shono-type oxidative cross-coupling has been developed by merging copper catalysis and electrochemistry, affording C1-alkynylated tetrahydroisoquinolines with good to excellent enantioselectivity. The use of TEMPO as a co-catalytic redox mediator is crucial not only for oxidizing a tetrahydroisoquinoline to an iminium ion species but also for decreasing the oxidation potential of the reaction. A novel bisoxazoline ligand is also reported.
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A scalable enantioselective nickel-catalyzed electrochemical reductive homocoupling of aryl bromides has been developed, affording enantioenriched axially chiral biaryls in good yield under mild conditions using electricity as a reductant in an undivided cell. Common metal reductants such as Mn or Zn powder resulted in significantly lower yields in the absence of electric current under otherwise identical conditions, underscoring the enhanced reactivity provided by the combination of transition metal catalysis and electrochemistry.
RESUMEN
A novel, hydrophilic and recyclable methoxypolyethylene glycol (PEG)-modulated s-triazine-based multifunctional Schiff base/N,P-ligand L9 was prepared and used in Pd-catalyzed Heck-type carbonylative coupling reactions, affording diverse chalcone derivatives and 1,4-dicarbonyl esters in good yields.
RESUMEN
Objective To evaluate the value of high-frequency ultrasound (HFUS) in diagnosing peripheral nerve compression in patients with rheumatoid arthritis (RA). Methods The upper limb nerves were evaluated by HFUS in 80 RA patients (RA group) and 60 non-RA patients (control group),then the incidence of peripheral nerve compression was recorded respectively. RA patients with/without neurological symptoms were compared in terms of age,disease course,Health Assessment Questionnaire Disability Index (HAQ-DI) score,and clinical disease activity index (CDAI). Results The incidence of upper limb nerve compression in RA group was significantly higher than that in control group(15.0% vs. 3.3%,P=0.046).The patients with nerve compression was older [(60.2±11.4)y vs.(49.2±7.9)y;t=2.343,P=0.039] and had longer disease course [(9.50±5.99) y vs. (5.88±3.87)y;t=2.639,P=0.023] and higher HAQ-DI score (1.58±0.75 vs.0.85±0.67;t=2.490,P=0.030). These two groups had no statistical differences in CDAI (14.50±11.68 vs.16.62±9.24;t=1.141,P=0.278).Conclusions Peripheral neuropathies are common extra-articular manifestations in RA patients. HFUS can be valuable in patients suspected of RA.