Enantioselective Ni-Catalyzed Electrochemical Synthesis of Biaryl Atropisomers.

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.

Nickel-Catalyzed Electrochemical Reductive Relay Cross-Coupling of Alkyl Halides to Aryl Halides.

A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which provides an alternative approach for the synthesis of 1,1-diarylalkanes.

Electrochemistry-Enabled Ir-Catalyzed Vinylic C-H Functionalization.

Synergistic use of electrochemistry and organometallic catalysis has emerged as a powerful tool for site-selective C-H functionalization, yet this type of transformation has thus far mainly been limited to arene C-H functionalization. Herein, we report the development of electrochemical vinylic C-H functionalization of acrylic acids with alkynes. In this reaction an iridium catalyst enables C-H/O-H functionalization for alkyne annulation, affording α-pyrones with good to excellent yields in an undivided cell. Preliminary mechanistic studies show that anodic oxidation is crucial for releasing the product and regeneration of an Ir(III) intermediate from a diene-Ir(I) complex, which is a coordinatively saturated, 18-electron complex. Importantly, common chemical oxidants such as Ag(I) or Cu(II) did not give significant amounts of the desired product in the absence of electrical current under otherwise identical conditions.

Electrochemical Radical Formyloxylation-Bromination, -Chlorination, and -Trifluoromethylation of Alkenes.

Given the versatility and value of the structurally diverse organohalides and CF3-containing compounds in organic synthesis, we reported a green, oxidant-free electrochemical method using undivided electrochemical cells for radical bromination, chlorination and trifluoromethylation-formyloxylation of the various alkenes with readily available halogen radical (NaCl, NaBr), trifluoromethyl radical (CF3SO2Na) sources, and DMF as formyloxylation reagents. The protocol is operationally simple and robust and the Cl-, Br- or CF3- was directly oxidized at the anode, obviating the need for exogenous chemical oxidants.

Nickel-Catalyzed Thiolation of Aryl Halides and Heteroaryl Halides through Electrochemistry.

Transition-metal-catalyzed coupling reactions are useful tools for synthesizing aryl sulfur compounds. However, conventional transition-metal-catalyzed thiolation of aryl bromides and chlorides typically requires the use of strong base under elevated reaction temperature. Herein, we report the first examples of nickel-catalyzed electrochemical thiolation of aryl bromides and chlorides in the absence of an external base at room temperature using undivided electrochemical cells.

Identification of active compounds from Caesalpinia sappan L. extracts suppressing IL-6 production in RAW 264.7 cells by PLS.

ETHNOPHARMACOLOGICAL RELEVANCE: Caesalpinia sappan L. is distributed in Southeast Asia and also used as herbal medicine for the treatment of various diseases such as burning sensations, leprosy, dysentery, osteoarthritis and rheumatoid arthritis (RA). The overproduction of IL-6 plays an important role in the prognosis of RA, but the active compounds from the extracts of Caesalpinia sappan L. suppressing IL-6 production remain unknown. AIMS OF THE STUDY: Identifying the main active compounds of Caesalpinia sappan L. extracts inhibiting the IL-6 production in LPS-stimulated RAW 264.7 cells by partial least squares (PLS). MATERIALS AND METHODS: Sixty-four samples with different proportions of compounds were prepared from Caesalpinia sappan L. by supercritical CO2 fluid extraction (SCFE) and refluxing. Each of 64 samples was applied to RAW 264.7 cells with LPS to evaluate whether IL-6 production by LPS is affected by addition of each sample. The IL-6 production in medium was determined by ELISA and the inhibitory activity of each sample was analyzed. In addition, the fingerprints of these 64 samples were also established by ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC-MS). We used the PLS, a simplified method, to evaluate the results from IL-6 production and fingerprints. RESULTS: Each of 64 samples markedly suppressed LPS-induced IL-6 production in RAW cells. The fingerprints by UPLC-MS clearly revealed variations among 64 samples produced in different extract conditions. The PLS analysis with IL-6 production and fingerprints by UPLC-MS suggested that the peaks 71, 93, 150, 157, 168 have more influence on the inhibitory activity of Caesalpinia sappan L. extracts. The peaks 71, 93, 150 are likely representing sappanone A, protosappanin E and neoprotosappanin, respectively. The peaks 157 and 168 are still at large. CONCLUSION: This is the first report that sappanone A, protosappanin E, neoprotosappanin and two unidentified compounds can be considered as possible active compounds that might inhibit IL-6 production. Further studies are needed to confirm the effectiveness of these five compounds on IL-6 production and possible mechanism.