Manoj V. Mane

Construction of Crystalline 2D Covalent Organic Frameworks with Remarkable Chemical (Acid/Base) Stability via a Combined Reversible and Irreversible Route

Two new chemically stable [acid and base] 2D crystalline covalent organic frameworks (COFs) (TpPa-1 and TpPa-2) were synthesized using combined reversible and irreversible organic reactions. Syntheses of these COFs were done by the Schiff base reactions of 1,3,5-triformylphloroglucinol (Tp) with p-phenylenediamine (Pa-1) and 2,5-dimethyl-p-phenylenediamine (Pa-2), respectively, in 1:1 mesitylene/dioxane. The expected enol-imine (OH) form underwent irreversible proton tautomerism, and only the keto-enamine form was observed. Because of the irreversible nature of the total reaction and the absence of an imine bond in the system, TpPa-1 and TpPa-2 showed strong resistance toward acid (9 N HCl) and boiling water. Moreover, TpPa-2 showed exceptional stability in base (9 N NaOH) as well.

Nuclear blebbing of biologically active organoselenium compound towards human cervical cancer cell (HeLa): in vitro DNA/HSA binding, cleavage and cell imaging studies.

New pharmacophore organoselenium compound (1) was designed, synthesized and characterized by various spectroscopic methods (IR, ESI-MS, (1)H, (13)C and (77)Se NMR) and further confirmed by X-ray crystallography. Compound 1 consists of two 3,5-bis(trifluoromethyl)phenyl units which are connected to the selenium atom via the organometallic C-Se bond. In vitro DNA binding studies of 1 was investigated by absorption and emission titration methods which revealed that 1 recognizes the minor groove of DNA in accordance with molecular docking studies with the DNA duplex. Gel electrophoretic assay demonstrates the ability of 1 to cleave pBR322 DNA through hydrolytic process which was further validated by T4 religation assay. To understand the drug-protein interaction of which ultimate molecular target was DNA, the affinity of 1 towards HSA was also investigated by the spectroscopic and molecular modeling techniques which showed hydrophobic interaction in the subdomain IIA of HSA. Furthermore, the intracellular localization of 1 was evidenced by cell imaging studies using HeLa cells.

Au(I)/Ag(I) co-operative catalysis: interception of Ag-bound carbocations with α-gold(I) enals in the imino-alkyne cyclizations with N-allenamides

A co-operative Au(i)/Ag(i) catalyst system has been developed to utilize N-allenamides as nucleophilic enal equivalents for the interceptive capturing of incipient carbocations generated through π-acid-triggered imino-alkyne cyclization. The salient features include the in situ generation of silver-bound carbocations (from iminoalkynes), α-gold(i) enals (from N-allenamides) and union of these two species to form indolizines with the regeneration of Au and Ag catalysts.

Computational study of metal free alcohol dehydrogenation employing frustrated lewis pairs.

The catalysis of acceptorless alcohol dehydrogenation (AAD) is an important area of research. Transition metal-based systems are known to be effective catalysts for this reaction, but developing metal free catalytic systems would lead to highly desirable cheaper and greener alternatives. With this in mind, this computational study investigates design strategies than can lead to metal free frustrated Lewis pairs (FLPs) that can be employed for AAD catalysis. A careful study of 36 different proposed FLP candidates reveals that several new FLPs can be designed from existing, experimentally synthesized FLPs that can rival or be even better than state-of-the-art transition metal-based systems in catalyzing the alcohol dehydrogenation process.

Exploring the Potential of Doped Zero-Dimensional Cages for Proton Transfer in Fuel Cells: A Computational Study

Calculations with density functional theory (DFT) and MP2 have been done to investigate the potential of recently synthesized durable zero-dimensional (OD) nitrogen-based cage structures to perform as efficient proton-exchange membranes (PEMs) in fuel cells. Our calculations suggest that the hydrogenated 0-D cages, in combination with hydrogen-bonding 1,2,3- and 1,2,4-triazole molecules, would perform as highly efficient PEMs. The results are important in the context of the need for efficient PEMs for fuel cells, especially at higher temperatures (greater than 120 °C) where conventional water-based PEMs such as Nafion have been found to be ineffective.

Computational survey of ligand properties on iron(III)–iron(II) redox potential: exploring natural attenuation of nitroaromatic compounds

This study is a computational investigation of the ligand effect on the redox potential of iron redox couple aimed at screening these systems for novel applications. The influence of common and naturally available organic compounds with diverse ligand characteristics (nature of donor site, chelation, pre-organization, degree of back acceptance) on the redox potential of iron(III)–iron(II) redox couple has been theoretically calculated using an appropriate level of density functional theory (DFT). The DFT calculated redox potentials of iron complexes are explored to supplement, corroborate, and predict the experimental behavior of the studied systems towards environmental reduction of nitroaromatic compounds to corresponding anilines. The comparative avidity of iron complexes with cysteine derivatives for the reduction of nitroaromatic compounds has been theoretically explored and based on structure–activity relationship; new iron complexes with a range of reactivity and enhanced ability towards nitroaromatic reduction have been predicted.Graphical abstract

Secondary Interactions Arrest the Hemiaminal Intermediate To Invert the Modus Operandi of Schiff Base Reaction: A Route to Benzoxazinones

Discovered by Hugo Schiff, condensation between amine and aldehyde represents one of the most ubiquitous reactions in chemistry. This classical reaction is widely used to manufacture pharmaceuticals and fine chemicals. However, the rapid and reversible formation of Schiff base prohibits formation of alternative products, of which benzoxazinones are an important class. Therefore, manipulating the reactivity of two partners to invert the course of this reaction is an elusive target. Presented here is a synthetic strategy that regulates the sequence of Schiff base reaction via weak secondary interactions. Guided by the computational models, reaction between 2,3,4,5,6-pentafluoro-benzaldehyde with 2-amino-6-methylbenzoic acid revealed quantitative (99%) formation of 5-methyl-2-(perfluorophenyl)-1,2-dihydro-4H-benzo[d][1,3]oxazin-4-one (15). Electron donating and electron withdrawing ortho-substituents on 2-aminobenzoic acid resulted in the production of benzoxazinones 9-36. The mode of action was tracked using low temperature NMR, UV-vis spectroscopy, and isotopic (18O) labeling experiments. These spectroscopic mechanistic investigations revealed that the hemiaminal intermediate is arrested by the hydrogen-bonding motif to yield benzoxazinone. Thus, the mechanistic investigations and DFT calculations categorically rule out the possibility of in situ imine formation followed by ring-closing, but support instead hydrogen-bond assisted ring-closing to prodrugs. This unprecedented reaction represents an interesting and competitive alternative to metal catalyzed and classical methods of preparing benzoxazinone.

Experimental and Computational Study of the (Z)-Selective Formation of Trisubstituted Olefins and Benzo-Fused Oxacycles from the Ruthenium-Catalyzed Dehydrative C–H Coupling of Phenols with Ketones

The cationic Ru-H complex was found to be an effective catalyst for the dehydrative C-H coupling of phenols with ketones to form the trisubstituted olefin products. The coupling of phenol with linear ketones led to highly stereoselective formation of the ( Z)-olefin products. The dehydrative coupling of phenol with enones and diones efficiently formed the benzopyrene and related oxacyclic derivatives. The reaction of 3,5-dimethoxyphenol with cyclohexanone-2,2,6,6- d4 showed a significant H/D exchange to both vinyl and α-CH2 positions on the olefin product (72-75% D). A significant carbon isotope effect was observed on the ortho-arene carbon of the olefin product. The free energies of intermediate species for the entire catalytic cycle were successfully computed by using the DFT method. The DFT study revealed that the E/ Z stereoselectivity is a result of the energy difference in the insertion step of ortho-metalated phenol to an enol form of the ketone substrate (ΔΔ E = 9.6 kcal/mol). The coupling method provides a direct catalytic C-H olefination method for ketones to form trisubstituted olefins without employing any reactive reagents or forming any wasteful byproducts.