Enantioselective Amination of 3-Substituted-2-benzofuranones via Non-covalent N-Heterocyclic Carbene Catalysis.

Herein, an efficient method for asymmetric α-amination of 2-benzofuranones with N-heterocyclic carbene (NHC) catalysis is reported. The process is based on non-covalent interaction of NHC with substrate, facilitating the formation of a chiral ion-pair that encompasses enolate and azolium salt. The activated enolate adds to an electrophilic amine source with sufficient facial control to furnish an enantioenriched product having an amine substituted quaternary stereocenter. The process displays a broad substrate scope. A preparative scale synthesis has been achieved. Preliminary mechanistic investigations based on experimental and DFT studies suggest a reaction pathway that involves non-covalent substrate/NHC interactions and essentially implicate the role of π-π interaction in diastereomeric transition states for stereo-chemical discrimination.

Metal-Ligand Cooperativity in MnI -Catalysed N-Formylation of Secondary Amides and Lactams Using CO2 at Room Temperature.

A MnI catalyst featuring redox-active tridentate phenalenyl (PLY) ligand has been used for catalytic N-formylation of secondary amides and lactams under 1 atm CO2 as a C1 source at room temperature for the first time. The protocol is applicable to a wide range of secondary amides including heterocycles, bio-active cinnamide derivatives and the diversification of therapeutic molecules. In-depth mechanistic investigations based on experimental outcomes and DFT calculations suggested an unconventional metal-ligand cooperation, where a ligand-centred radical plays a crucial role in initiating the reaction process.

The Role of Copper Salts and O2 in the Mechanism of C≡N Bond Activation for Facilitating Nitrogen Transfer Reactions.

C≡N bond scission can be a potential avenue for the functionalization of chemical bonds. We have conducted a computational study, using density functional theory (DFT) and ab initio multireference CASSCF methods, to unravel the intricate mechanistic pathways traversed in the copper-promoted, dioxygen-assisted reaction for the formation of aryl isocyanate species from aryl aldehyde. This aryl isocyanate species acts as an active species for C≡N bond cleavage of coordinated cyanide anion enabling nitrogen transfer to various aldehydes. Electronic structure analysis revealed that under all the reaction conditions radical-based pathways are operative, which is in agreement with the experimental findings. The major driving force is a CuII/I redox cycle initiated by single-electron transfer from the carbon center of the nitrile moiety. Our study reveals that the copper salts act as the "electron pool" in this unique nitrogen transfer reaction forming an aryl isocyanate species from aryl aldehydes.

Reduced graphene oxide (rGO) aerogel: Efficient adsorbent for the elimination of antimony (III) and (V) from wastewater.

3D porous, thin sheet-like rGO aerogel was fabricated to explore its antimony (Sb) removal potential from wastewater. Langmuir isothermal and pseudo-second-order kinetic model best-suited the adsorption process. The maximum adsorption capacities were 168.59 and 206.72 mg/g for Sb (III and V) at pH 6.0 respectively. The thermodynamic parameters designated the process to be thermodynamically spontaneous, endothermic reaction, a result of dissociative chemisorption. The rGO aerogel bestowed good selectively among competing ions and reusability with 95% efficiency. rGO posed excellent practicability with Sb-spiked tap water and fixed-bed column experiments showing 97.6% of Sb (III) (3.6 µg/L) and 96.8% of Sb (V) (4.7 µg/L) removal from tap water and from fixed column bed experiments breakthrough volumes (BV) for the Sb (III) and Sb (V) ions were noted to be 540 BV and 925 BV respectively, until 5 ppb, which are below the requirement of MCL for Sb in drinking water (6 µg/L). XPS and DFT analyses explained adsorption mechanism and depicted a higher affinity of Sb (V) towards rGO surface than Sb (III).