Magnetically Recyclable Borane Lewis Acid Catalyst for Hydrosilylation of Imines and Reductive Amination of Carbonyls.

Fluorinated arylborane-based Lewis acid catalysts have shown remarkable activity and serve as ideal examples of transition metal-free catalysts for diverse organic transformations. However, their homogeneous nature poses challenges in terms of recyclability and separation from reaction mixtures. This work presents an efficient technique for the heterogenization of boron Lewis acid catalysts by anchoring Piers' borane to allyl-functionalized iron oxide. This catalyst demonstrates excellent activity in the hydrosilylation of imines and the reductive amination of carbonyls using various silanes as reducing agents under mild reaction conditions. The catalyst exhibits broad tolerance towards a wide range of functional substrates. Furthermore, it exhibits good recyclability and can be easily separated from the products using an external magnetic field. This work represents a significant advance in the development of sustainable heterogenous metal-free catalysts for organic transformations.

A Single Terminal [NiII-OH] Catalyst for Direct Julia-Type Olefination and α-Alkylation Involving Sulfones and Alcohols.

A terminal [NiII-OH] complex 1, supported by triflamide-functionalized NHC ligands, showed divergent reactivity for the reaction of sulfone with alcohol, contingent on base concentration, temperature, and time. Julia-type olefination of alcohols with sulfones was achieved using one equiv. of base, whereas lowering base loading to 0.5 equiv. afforded α-alkylated sulfones. Besides excellent substrate scope and selectivity, biologically active stilbene derivatives DMU-212, pinosylvin, resveratrol, and piceatannol were synthesized in high yield under Julia-type olefination conditions. An extensive array of controlled experiments and DFT calculations provide valuable insight on the reaction pathway.

Synchronous Proton-Hydride Transfer by a Pyrazole-Functionalized Protic Mn(I) Complex in Catalytic Alcohol Dehydrogenative Coupling.

A series of Mn(I) complexes Mn(L1 )(CO)3 Br, Mn(L2 )(CO)3 Br, Mn(L1 )(CO)3 (OAc) and Mn(L3 )(CO)3 Br [L1 =2-(5-tert-butyl-1H-pyrazol-3-yl)-1,8-naphthyridine, L2 =2-(5-tert-butyl-1H-pyrazol-3-yl)pyridine, L3 =2-(5-tert-butyl-1-methyl-1H-pyrazol-3-yl)-1,8-naphthyridine] were synthesized and fully characterized. The acid-base equilibrium between the pyrazole and the pyrazolato forms of Mn(L1 )(CO)3 Br was studied by 1 H NMR and UV-vis spectra. These complexes are screened as catalysts for acceptorless dehydrogenative coupling (ADC) of primary alcohols and aromatic diamines for the synthesis of benzimidazole and quinoline derivatives with the release of H2 and H2 O as byproducts. The protic complex Mn(L1 )(CO)3 Br shows the highest catalytic activity for the synthesis of 2-substituted benzimidazole derivatives with broad substrate scope, whereas a related complex [Mn(L3 )(CO)3 Br], which is devoid of the proton responsive ß-NH unit, shows significantly reduced catalytic efficiency validating the crucial role of the ß-NH functionality for the alcohol dehydrogenation reactions. Control experiments, kinetic and deuterated studies, and density functional theory (DFT) calculations reveal a synchronous hydride-proton transfer by the metal-ligand construct in the alcohol dehydrogenation step.

Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides.

The inevitable emission of carbon dioxide (CO2 ) due to the burning of a substantial amount of fossil fuels has led to serious energy and environmental challenges. Metal-based catalytic CO2 transformations into commodity chemicals are a favorable approach in the CO2 mitigation strategy. Among these transformations, selective hydrogenation of CO2 to methanol is the most promising process that not only fulfils the energy demands but also re-balances the carbon cycle. The investigation of CO2 adsorption on the surface of heterogeneous catalyst is highly important because the formation of various intermediates which determines the selectivity of product. Transition metal carbides (TMCs) have received considerable attention in recent years because of their noble metal-like reactivity, ceramic-like properties, high chemical and thermal stability. These features make them excellent catalytic materials for a variety of transformations such as CO2 adsorption and its conversion into value-added chemicals. Herein, the catalytic properties of TMCs are summarize along with synthetic methods, CO2 binding modes, mechanistic studies, effects of dopant on CO2 adsorption, and carbon/metal ratio in the CO2 hydrogenation reaction to methanol using computational as well as experimental studies. Additionally, this Review provides an outline of the challenges and opportunities for the development of potential TMCs in CO2 hydrogenation reactions.

New simple molecular fluorescent probes for rapid and highly selective sensing of hydrazine by aggregate-induced emission.

With an aim towards the design of efficient and straightforward fluorescent probes for hydrazine, the synthesis of (2-acetoxyaryl) methylene diacetate derivatives (1-4) was carried out by reacting substituted aromatic α-hydroxy aldehydes with acetyl chloride and sodium acetate in excellent yields. As a preliminary investigation, the ability of probe 1 was examined for the detection of substituted aliphatic and aromatic amines, amino acids, and other ions in Britton-Robinson buffer solution (50 mM, water/ethanol v/v of 99/1 at pH 7.4). Probe 1 selectively exhibited an intense blue fluorescence with hydrazine in less than 2 minutes, whereas light green or no fluorescence was noticed with substituted amines and amino acids. Among all the probes employed (1-4) in the present study, probes 1 and 2 were found efficient towards the rapid detection of hydrazine. Furthermore, the fluorescence sensing ability of probes 1 and 2 was tested not only under varying pH conditions but also by varying water-fraction from 0-99%. Moreover, the detection limits of hydrazine using 1 and 2 were found as 8.4 and 8.7 ppb, respectively, which is less than the acceptable limit as per the standards of the US Environment Protection Agency. In this contribution, the probes 1 and 2 demonstrate rapid, selective, sensitive, and ratiometric detection of highly toxic hydrazine by OFF-ON fluorescence switch in water samples as well as living cells.

A DFT study of inclusion complexes of substituted calix[n]arenes with dasatinib and lapatinib.

Herein, we have presented the results of Density Functional Theory (DFT) based calculations of inclusion complexes of lapatinib and dasatinib with calix[n]arene macrocycles. A total of 48 calix [n]arene complexes were modeled via considering varied ring sizes (n = 4,5,6,8) and upper-rim functionalization viz. SO3H, tert-Butyl, iso-Propyl, COOH, C2H5OH, and C2H5NH2. From the results of multilevel molecular docking, DFT energetics, and reactivity descriptors; it has been demonstrated that dasatinib form optimal complexes with calix 4f, 3f (-35 to -40 kcal/mol). Moreover, for lapatinib, hosts 3f, 4a, 1f, 3d have the capability to generate promising complexes (>35 kcal/mol). Based on counterpoise corrected binding energies (Ebind) and global reactivity descriptors, we anticipate that the proposed complexes can vitally be used as analogous to carrier-mediated-drug-delivery.

Probing the opportunities for designing anthelmintic leads by sub-structural topology-based QSAR modelling.

A quantitative structure-activity (QSAR) model has been developed for enriched tubulin inhibitors, which were retrieved from sequence similarity searches and applicability domain analysis. Using partial least square (PLS) method and leave-one-out (LOO) validation approach, the model was generated with the correlation statistics of [Formula: see text] and [Formula: see text] of 0.68 and 0.69, respectively. The present study indicates that topological descriptors, viz. BIC, CH_3_C, IC, JX and Kappa_2 correlate well with biological activity. ADME and toxicity (or ADME/T) assessment showed that out of 260 molecules, 255 molecules successfully passed the ADME/T assessment test, wherein the drug-likeness attributes were exhibited. These results showed that topological indices and the colchicine binding domain directly influence the aetiology of helminthic infections. Further, we anticipate that our model can be applied for guiding and designing potential anthelmintic inhibitors.

Exploration of interaction zones of ß-tubulin colchicine binding domain of helminths and binding mechanism of anthelmintics.

Numerous studies postulated the possible modes of anthelmintic activity by targeting alternate or extended regions of colchicine binding domain of helminth ß-tubulin. We present three interaction zones (zones vide -1 to -3) in the colchicine binding domain of Haemonchus contortus (a helminth) ß-tubulin homology model and developed zone-wise structure-based pharmacophore models coupled with molecular docking technique to unveil the binding hypotheses. The resulted ten structure-based hypotheses were then refined to essential three point pharmacophore features that captured recurring and crucial non-covalent receptor contacts and proposed three characteristics necessary for optimal zone-2 binding: a conserved pair of H bond acceptor (HBA to form H bond with Asn226 residue) and an aliphatic moiety of molecule separated by 3.75±0.44Å. Further, an aliphatic or a heterocyclic group distant (11.75±1.14Å) to the conserved aliphatic site formed the third feature component in the zone-2 specific anthelmintic pharmacophore model. Alternatively, an additional HBA can be substituted as a third component to establish H bonding with Asn204. We discern that selective zone-2 anthelmintics can be designed effectively by closely adapting the pharmacophore feature patterns and its geometrical constraints.