In this report, we have synthesized two NCS pincer ligands by the Schiff base reaction of 3-((phenylthio)methoxy)benzaldehyde (P) with alkyl amines (tbutylamine (L1) and 1-adamantylamine (L2)). The palladium pincer complexes (tbutylamine = C1 and 1-adamantylamine = C2) of these ligands were synthesized by their reaction with PdCl2(CH3CN)2. The newly synthesized ligands and complexes were characterized using various techniques such as 1H, 13C{1H} Nuclear Magnetic Resonance (NMR), Ultraviolet–visible (UV-Visible), Fourier Transform Infrared (FTIR) Spectroscopy, and High-Resolution Mass Spectrometry (HRMS). The structure of ligand and its coordination mode with palladium precursor were studied with the help of single-crystal X-ray diffraction. The complexes showed distorted square planar geometry around the palladium center. The palladium pincer complexes were used as catalysts for the regioselective cross-dehydrogenative alkenation of 2-arylthiophene derivatives. The complex C2, where sterically bulky adamantyl ligand is part of the side arm showed a higher yield of alkenation reaction. Only 2.5 mol% catalyst loading was sufficient to achieve 74-95% yields of desired products with excellent functional group tolerance under mild reaction conditions. The poisoning experiments (PPh3 and Hg) showed the homogeneous nature of the catalytic process. The plausible mechanism of the reaction was proposed based on the control experiments and time-dependent HRMS studies.

Halohydrin dehalogenases (HHDHs) have demonstrated significant potential as biocatalysts for synthesizing industrial heterocyclic compounds and chiral alkanolamines from aromatic substrates with NaOCN that are not feasible through chemosynthesis. To further study the HHDH reaction in real industrial applications, a diverse panel of HHDHs has been screened for their ability to convert aliphatic cyclohexene oxide. By using the best HHDH variant in form of a whole cell biocatalyst, a novel chemical process, regulated by the cascaded chemoenzymatic reactions for pilot-scale ring-opening reactions, has been successfully developed.  Using the best HHDH hit in whole-cell form provides a viable bio-catalytic approach for the synthesis of related fine chemicals. Our research provides a promising strategy for scaling up non-native ring-opening reactions from the laboratory to industrial applications.

We study the hyperactivation of α-chymotrypsin (α-ChT) here, using acrylate-derived PCEA polymer. Enzyme activity assays revealed a pronounced enzyme hyperactivation capacity being superior to widespread PAA polymers. In a combined experimental and computational study, we investigate α-ChT/polymer interactions to elucidate the hyperactivation mechanism.

Abstract

We study the hyperactivation of α-chymotrypsin (α-ChT) using the acrylate polymer poly(2-carboxyethyl) acrylate (PCEA) in comparison to the commonly used poly(acrylic acid) (PAA). The polymers are added during the enzymatic cleavage reaction of the substrate N-glycyl-L-phenylalanine p-nitroanilide (GPNA). Enzyme activity assays reveal a pronounced enzyme hyperactivation capacity of PCEA, which reaches up to 950 % activity enhancement, and is significantly enhanced to PAA (revealing an activity enhancement of approx. 450 %). In a combined experimental and computational study, we investigate α-ChT/polymer interactions to elucidate the hyperactivation mechanism of the enzyme. Isothermal titration calorimetry reveals a pronounced complexation between the polymer and the enzyme. Docking simulations reveal that binding of polymers significantly improves the binding affinity of GPNA to α-ChT. Notably, a higher binding affinity is found for the α-ChT/PCEA compared to the α-ChT/PAA complex. Further molecular dynamics (MD) simulations reveal changes in the size of the active site in the enzyme/polymer complexes, with PCEA inducing a more pronounced alteration compared to PAA, facilitating an easier access for the substrate to the active site of α-ChT.

This review highlights the recent advances in utilizing epoxides as alkylating reagents in transition-metal-catalyzed C−H alkylation, along with its associated synthetic applications in organic synthesis.

Abstract

The alkylation of arenes is one of the most fundamental transformations in synthetic chemistry and the transition-metal-catalyzed direct C−H alkylation represents a straightforward and attractive approach from both atom and step-economy perspectives. Epoxides, the smallest three-membered saturated O-heterocycles that can be easily prepared in racemic or enantioenriched forms, are highly useful building blocks for the synthesis of complex organic molecules. Owing to their inherent high ring-strain, epoxides readily undergo ring-opening reactions and have been used as alkylating reagents for C−H alkylation catalyzed by transition metals. This review summarizes recent advances in utilizing epoxides as alkylating reagents in transition-metal-catalyzed C−H alkylation as well as their synthetic applications in organic synthesis.

A series of twelve [fac-Mn(R₂bpy)(CO)₃(CH₃CN)]⁺ pre-catalysts with systematically varied second coordination sphere functionality for the proton-coupled electrocatalytic reduction of CO₂ are reported, whereby a structure-determined shift in catalytic pathway is demonstrated and product selectivity is tuned from CO to competing HCO₂H and H₂ production.

Abstract

A series of twelve second coordination sphere (SCS) functionalized manganese tricarbonyl bipyridyl complexes are investigated for their electrocatalytic CO₂ reduction properties in acetonitrile. A qualitative and quantitative assessment of the SCS functional groups is discussed with respect to the catalysts’ thermodynamic and kinetic efficiencies, and their product selectivities. In probing a broad scope of functional groups, it is clear that only the aprotic ortho-arylester SCS is capable of promoting the highly desired low-overpotential proton-transfer electron-transfer (PT-ET) pathway for selective CO production. The ortho-phenolic analogues cause an increase in overpotential with a product selectivity favoring H₂ evolution, consistent with a high-overpotential pathway via the anionic [Mn−H]⁻ intermediate. Alternative aprotic Lewis base functional groups such as trifluoromethyl, morpholine and acetamide are shown to also be capable of intermediate manganese hydride generation. The tertiary amine substituent, 2-morpholinophenyl, exhibits a desirable product distribution characteristic of syn-gas (CO : H₂=30 : 48) with an impressive turnover frequency, while the secondary amine group, 2-acetamidophenyl, induces a notable shift in selectivity with a faradaic yield of 55 % for the formate (HCO₂ ⁻) product. In addition to their catalytic properties, cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC) studies are presented to probe pre-catalyst electronic properties and the two-electron reduction activation pathway.

Low-valent chromium catalysts are cheap and less toxic compared to other transition metal catalysts. Here in, we reported a ligand-free chromium(III)-catalyzed manganese reductive cross-coupling of unactivated alkyl electrophiles, such as alkyl sulfonates and alkyl chlorides, with trisulfide dioxides as thiolation agents to form carbon-sulfur bonds. The powerful method featured ample substrate scope and wide functional group tolerance, constructing a large number of unsymmetrical disulfides under simple conditions.

The escalating demand for fossil fuels has raised environmental concerns, urging the exploration of biosynthetic pathways for renewable hydrocarbon fuels. Terminal alkenes (α-alkenes) emerge as "drop-in" compatible fuels and chemicals, holding the potential to replace traditional fossil fuels. Fatty acid decarboxylases present a promising route for converting fatty acids into α-alkenes, underscoring the imperative need for comprehending the catalytic mechanisms governing these enzymes in the quest for renewable biofuel production. The reported fatty acid decarboxylases entail the involvement of heme and non-heme iron cofactors in the redox process. In this review, we summarize the reaction mechanisms of four iron-dependent fatty acid decarboxylases (OleTJE, OleTPRN, UndA, and UndB), providing a critical analysis of the factors influencing chemical selectivity and catalytic performance.

Herein, we report a phosphine free novel ruthenium NNN based pincer complex that can act as a highly efficient catalyst for N-methylation of amines and direct N-methylation of nitroarenes using methanol as a C1 source under mild reaction conditions following the borrowing-hydrogen approach.

Abstract

A novel phosphine-free ruthenium pincer complex based on an NNN pincer ligand has been prepared and fully characterized. The complex was subsequently employed as an efficient catalyst for the N-methylation of amines and the direct N-methylation of nitroarenes using methanol as a C1 source under mild reaction conditions following the borrowing-hydrogen approach. Both of the catalytic transformations were performed with only catalytic amounts of base under closed air conditions without using any other additives.

We report on the fixation of CO₂ to prebiotic intermediates over mesoporous silica-supported Co−Fe catalysts. Supported catalysts convert CO₂ to various gaseous and liquid products under simulated hydrothermal vent conditions. Among different catalysts, a supported Co−Fe alloy with the same composition as the natural mineral wairauite yields the highest concentrations of formate and acetate, which are key intermediates in the acetyl-coenzyme A pathway.

Abstract

To test the ability of geochemical surfaces in serpentinizing hydrothermal systems to catalyze reactions from which metabolism arose, we investigated H₂-dependent CO₂ reduction toward metabolic intermediates over silica-supported Co−Fe catalysts. Supported catalysts converted CO₂ to various products at 180 °C and 2.0 MPa. The liquid product phase included formate, acetate, and ethanol, while the gaseous product phase consisted of CH₄, CO, methanol, and C₂−C₇ linear hydrocarbons. The 1/1 ratio CoFe alloy with the same composition as the natural mineral wairauite yielded the highest concentrations of formate (6.0 mM) and acetate (0.8 mM), which are key intermediates in the acetyl-coenzyme A (acetyl-CoA) pathway of CO₂ fixation. While Co-rich catalysts were proficient at hydrogenation, yielding mostly CH₄, Fe-rich catalysts favored the formation of CO and methanol. Mechanistic studies indicated intermediate hydrogenation and C−C coupling activities of alloyed CoFe, in contrast to physical mixtures of both metals. Co in the active site of Co−Fe catalysts performed a similar reaction as tetrapyrrole-coordinated Co in the corrinoid iron-sulfur (CoFeS) methyl transferase in the acetyl-CoA pathway. In a temperature range characteristic for deeper regions of serpentinizing systems, oxygenate product formation was favored at lower, more biocompatible temperatures.

This review introduces the in-situ characterization techniques frequently used in the electrocatalytic NO₃ ⁻ reduction to NH₃ (ENO₃RA), summarizes five pathways for converting *NO to NH₃ during ENO₃RA on Cu-based catalysts. And the application of the in-situ techniques is presented as an example of Cu-based catalysts, which are sorted out in terms of composition and structure.

Abstract

The excess nitrate (NO₃ ⁻) in water mainly comes from agricultural fertilization and industrial wastewater, which breaks the nitrogen balance and poses a serious threat to the environment and human health. Driven by renewable energy, the electrocatalytic NO₃ ⁻ reduction to ammonia (NH₃) (ENO₃RA) is an environmentally friendly and sustainable technology. Due to its special structure, copper (Cu) is currently one of the best catalysts for ENO₃RA, but the reaction mechanism and the structure–activity relationships of catalysts are still not clear enough. In-situ characterization is a powerful tool to gain insight into the reaction process. This review introduces several types of in-situ techniques such as in-situ XAS, in-situ FTIR and in-situ DEMS, summarizes five pathways for converting *NO as the key intermediate to NH₃ during ENO₃RA on Cu-based catalysts. The research progress of Cu-based electrocatalysts in recent years is sorted out from the aspects of composition and structure, and the catalytic mechanisms are discussed with the help of in-situ characterization technologies. This review would be of help to provide reference characterization methods for exploring the mechanism and the design of electrocatalysts for ENO₃RA.