Directing Group Strategy for the Isolation of Organoselenium(VI) Benzoselenonates: Metal-Free Catalysts for Hydrogen Evolution Reaction.

The exploration of fourth-period organoelements, particularly organoseleniums in their highest VI oxidation state, is limited owing to their stability and synthesis. Herein, the isolation of a new class of quinolinyl-embedded, hexavalent selenium(VI) benzoselenonates has been discussed and further evaluated for a metal-free electrocatalytic hydrogen evolution reaction (HER). The Se(VI) benzoselenonates exhibited high Faradaic efficiency (F.E.) of metal-free H2 gas production up to 86% with a very good turnover number (TON) up to 43 and moderate overpotential (η) of 500 mV; in the presence of mild acetic acid source in a less deprotonating DMF solvent. Taken together with various (NMR, UV-vis, and EPR) spectroscopic and DFT computation studies, a plausible HER pathway is proposed, which suggests that the electrochemical reduction of quinolinyl ring is the initiation step and Se(VI) acts as the reaction site by involving a hydridic type of intermediate for the electrochemical H2 gas generation.

Bidentate Ligand Driven Intramolecularly Te O Bonded Organotellurium Cations from Synthesis, Stability to Catalysis.

A new series of unsymmetrical phenyl tellurides derived from 2-N-(quinolin-8-yl) benzamide ligand has been synthesized in a practical manner by the copper-catalyzed method by using diaryl ditelluride and Mg as a reductant at room temperature. In order to augment the Lewis acidity of these newly formed unsymmetrical monotellurides, these have been transformed into corresponding unsymmetrical 2-N-(quinolin-8-yl)benzamide tellurium cations. Subsequently, these Lewis acidic tellurium cations were used as chalcogen bonding catalysts, enabling the synthesis of various substituted 1,2-dihydroquinolines by activating ketones with anilines under mild conditions. Moreover, the synthesized 2-N-(quinolin-8-yl)benzamide phenyl tellurium cation has also catalyzed the formation of ß-amino alcohols in high regioselectivity by effectively activating epoxides at room temperature. Mechanistic insight by 1 H and 19 F NMR study, electrostatic surface potential (ESP map), control reaction in which tellurium cation reacted explosively with epoxide, suggested that the enhanced Lewis acidity of tellurium center seems responsible for efficient catalytic activities under mild conditions enabling ß-amino alcohols with excellent regioselectivity and 1,2-dihydroquinolines with trifluoromethyl, nitro, and pyridylsubstitution, which were difficult to access.

2-Benzamide Tellurenyl Iodides: Synthesis and Their Catalytic Role in CO2 Mitigation.

Benzamide-derived organochalcogens (chalcogen=S, Se, and Te) have shown promising interest in biological and synthetic chemistry. Ebselen molecule derived from benzamide moiety is the most studied organoselenium. However, its heavier congener organotellurium is under-explored. Here, an efficient copper-catalyzed atom economical synthetic method has been developed to synthesize 2-phenyl-benzamide tellurenyl iodides by inserting a tellurium atom into carbon-iodine bond of 2-iodobenzamides in one pot with 78-95 % yields. Further, the Lewis acidic nature of Te center and Lewis basic nature of nitrogen of the synthesized 2-Iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides enabled them as pre-catalyst for the activation of epoxide with CO2 at 1 atm for the preparation of cyclic carbonates with TOF and TON values of 1447 h-1 and 4343, respectively, under solvent-free conditions. In addition, 2-iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides have also been used as pre-catalyst for activating anilines and CO2 to form a variety of 1,3-diaryl ureas up to 95 % yield. The mechanistic investigation for CO2 mitigation is done by 125 Te NMR and HRMS studies. It seems that the reaction proceeds via formation of catalytically active Te-N heterocycle, an ebtellur intermediate which is isolated and structurally characterized.

Blue Light Irradiated Metal-, Oxidant-, and Base-Free Cross-Dehydrogenative Coupling of C(sp2)-H and N-H Bonds: Amination of Naphthoquinones with Amines.

Herein, we report a blue-light-driven amination of C(sp2)-H bond of naphthoquinones and quinones with the N-H bond of primary and secondary amines for the synthesis of 2-amino-naphthoquinones and 2-amino-quinones. The coupling of naphthoquinones with a wide array of aliphatic, aromatic, chiral, primary, and secondary amines having electron donating (-CH3, -OCH3, -SCH3), withdrawing (-F, -Cl, -Br, -I), and CO2H, -OH, -NH2 groups with acidic protons selectively occurred to afford C-N coupled 2-amino-naphthoquinones in 60-99% yields and hydrogen gas as a byproduct in methanol solvent without using any additional reagents, additives, and oxidant under the blue light irradiation. Mechanistic insight by DFT computation, controlled experiments, kinetic isotopic effect, and substitution effect of the substrates suggest that the reaction proceeds by radical pathway in which naphthoquinone forms a highly oxidizing naphthoquinonyl biradical upon irradiation of blue light (457 nm). Consequently, electron transfer from electron-rich amine to an oxidizing naphthoquinonyl biradical leads to a naphthoquinonyl radical anion and aminyl radical cation, followed by proton transfer and delocalization leading to a carbon-centered naphthoquinonyl radical. The cross-coupling of naphthoquinonyl carbon-centered and aminyl nitrogen radicals forms a C-N bond, with subsequent elimination of hydrogen gas (which was also confirmed by GC-TCD), affording 2-amino-1,4-naphthoquinone under metal-, reagent-, base-, and oxidant-free conditions.

Isolation of monomeric copper(II) phenolate selenoether complexes using chelating ortho-bisphenylselenide-phenolate ligands and their electrocatalytic hydrogen gas evolution activity.

A series of novel copper(II) phenolate selenoether complexes have been synthesized and structurally characterized for the first time from copper(I) phenanthroline and various substituted ortho-bisphenylselenide-phenol chelating ligands. The synthesized complexes exhibit Jahn-Teller distortion in their geometry and varied from distorted square planar to distorted octahedral by varying the substituent in the bis-selenophenolate ligand. The synthesized complexes electrocatalyze the hydrogen evolution reaction (HER) with a faradaic efficiency of up to 89%, and it was observed that the distorted square pyramidal geometry is the optimum geometry for the maximum efficiency of these copper complexes.

Light-Driven Carbon-Carbon Coupling of α-sp3-CH of Aliphatic Alcohols with sp2-CH Bond of 1,4-Naphthoquinones.

Here, an α-selective Csp3-H bond functionalization of primary aliphatic alcohols with 1,4-naphthoquinones yielded Csp2-Csp2 coupled products driven by blue-LED light under catalyst, metal, base, and reagent-free conditions. In this transformation, cleavage of three C-H bonds (two sp3-C-H, one sp2-C-H, and one O-H) and four new bonds formed, leading to fluorescent 2-acylated-1,4-naphthohydroquinones.

The analgesic effect of bilateral ultrasound-guided erector spinae plane block in paediatric lower abdominal surgeries: A randomised, prospective trial.

BACKGROUND AND AIMS: This study aims to evaluate the analgesic effect of ultrasound-guided erector spinae plane block (ESPB) in paediatric lower abdominal surgeries. METHODS: Randomised, prospective trial. Forty patients, aged 2-10 years with the American Society of Anesthesiologists Score of I and II scheduled for elective lower abdominal surgery were included in the study. INTERVENTIONS: Patients were randomised into two groups as control group and ESPB group. Ultrasound-guided erector spinae plane block at L1 vertebral level was performed preoperatively using 0.5 ml/kg 0.25% bupivacaine (max 20 ml) for the patients in ESPB group. Analgesic requirements and time to first analgesic requirement were recorded and Face, Legs, Activity, Cry and Consolability (FLACC) scores for pain were recorded at 0, 1, 2, 3, 6, 12 and 24 h postoperatively. RESULTS: Forty patients were included in the final analyses. Significant difference was determined between the groups on post-operative morphine requirement and FLACC scores at 3 h and 6 h postoperatively (P < 0.05). Significant difference was also determined in time to first dose of rescue analgesia between the groups (P < 0.05). CONCLUSIONS: This study shows that the ESPB provides adequate post-operative analgesia in paediatric patients undergoing lower abdominal surgery.