Bifunctional Organic Catalysts Research Articles

L-Proline Catalyzed Knoevenagel Condensation of Aldehydes with Active Methylene Compounds and Their Molecular Modeling Studies for Anti-SARS CoV-2 Potentials

Introduction: An efficient one-pot synthesis of 2-alkylidene/arylidene derivatives was reported from active methylene compounds such as malononitrile/ethyl cyanoacetate/5-methyl-2,4- dihydro-3H-pyrazol-3-one and aldehydes in the presence of 10 mol% of L-proline (ethanol at room temperature). Methods: All derivatives were obtained in good to excellent yields. The structures of the synthesized compounds were confirmed from their FTIR (Fourier-transform infrared spectroscopy), 1H-NMR (Proton nuclear magnetic resonance), and mass spectroscopy. The importance of these compounds is predicted from their SAR (structure-activity relationship) study. Moreover, these newer compounds were further docked into various therapeutic targets of the SARS-CoV-2 (severe acute respiratory syndromerelated coronavirus) virus. Results: Results from our molecular docking suggest that these compounds have good inhibitory properties on the SARS- CoV-2 virus. Conclusion: L-proline (bifunctional organic catalyst) is found to be the best catalyst for the synthesis of different condensed products from active methylene compounds and aldehydes.

A DFT-design of single component bifunctional organocatalysts for the carbon dioxide/propylene oxide coupling reaction.

The aim of this work is to develop single-component bifunctional organic catalysts capable of effective coupling reactions between CO2 and propylene epoxide (PO) under mild conditions using density functional theory (DFT) calculations. The dual functionalities of the target catalysts come from their inclusion of a hydroxyl-containing electrophile and the nucleophilicity of iodide ion. In this respect, a series of hydroxyl-functionalized quaternary onium-based ionic liquids were studied using M062X-D3/def2-TZVP//M062X-D3/def2-SVPP model chemistry. The design of catalysts was based on tailoring two structural factors; the first one is the onium center of pnictogens (N, P, As, Sb and Bi), and the second one is the number of hydrogen bond donor groups (n = 1-3). The proposed catalysts were examined by investigation of their catalytic mechanisms to afford the cyclic carbonate. Additionally, the highest active transition state, along with the potential energy difference, was examined using non-covalent interaction (NCI) analysis. Also, the activation strain model (ASM) was used to explain the kinetic behavior of PO activation. The findings showed that the ring-opening step of PO is always the critical step of the reaction. Among the suggested catalysts, the results indicated that the dihydroxyl ammonium-based catalyst (2OH-NI) is a good choice for this catalysis under mild and solvent-free conditions.

Enantioselective Halolactonization Reactions using BINOL-Derived Bifunctional Catalysts: Methodology, Diversification, and Applications.

A general protocol is described for inducing enantioselective halolactonizations of unsaturated carboxylic acids using novel bifunctional organic catalysts derived from a chiral binaphthalene scaffold. Bromo- and iodolactonization reactions of diversely substituted, unsaturated carboxylic acids proceed with high degrees of enantioselectivity, regioselectivity, and diastereoselectivity. Notably, these BINOL-derived catalysts are the first to induce the bromo- and iodolactonizations of 5-alkyl-4( Z)-olefinic acids via 5- exo mode cyclizations to give lactones in which new carbon-halogen bonds are created at a stereogenic center with high diastereo- and enantioselectivities. Iodolactonizations of 6-substituted-5( Z)-olefinic acids also occur via 6- exo cyclizations to provide δ-lactones with excellent enantioselectivities. Several notable applications of this halolactonization methodology were developed for desymmetrization, kinetic resolution, and epoxidation of Z-alkenes. The utility of these reactions is demonstrated by their application to a synthesis of precursors of the F-ring subunit of kibdelone C and to the shortest catalytic, enantioselective synthesis of (+)-disparlure reported to date.

Enantioselective Synthesis of F-Ring Fragments of Kibdelone C via Desymmetrizing Bromolactonization of 1,4-Dihydrobenzoic Acid

We previously reported a bifunctional organic catalyst that promotes highly efficient enantioselective halolactonizations of a broad array of olefinic acids. As part of that work, we demonstrated the desymmetrization of a prochiral substrate through a catalytic enantioselective halolactonization, and we report herein the application of one such desymmetrization process to the syntheses of F-ring subunit synthons of (+)-kibdelone C.

Catalytic Enantioselective Addition of Indoles to Activated N-Benzylpyridinium Salts: Nucleophilic Dearomatization of Pyridines with Unusual C-4 Regioselectivity

The catalytic enantioselective dearomatization of pyridines with nucleophiles represents a direct and convenient access to highly valuable dihydropyridines. Available methods, mostly based on N-acylpyridinium salts, give addition to the C-2/C-6 of the pyridine nucleus, rendering 1,2-/1,6-dihydropyridines. Herein, we present an alternative approach to this type of dearomatization reaction, employing activated N-benzylpyridinium salts in combination with a bifunctional organic catalyst. Optically active 1,4-dihydropyridines resulting from the addition of the nucleophile (indole) to the C-4 of the pyridine nucleus are obtained as major products, rendering this method for nucleophilic dearomatization of pyridines complementary to previous approaches.

A Bi-Functional Organic Redox Catalyst for Rechargeable Lithium-Oxygen Batteries with Enhanced Performances

The Li-O2 battery provides the highest energy density among all rechargeable battery systems. To date, the large over-potentials during the oxygen reduction reaction and oxygen evolution reaction lead to low round-trip efficiency and short cycle life. Herein, we report a Li-O2 battery with outstanding performance. Application of a bi-functional organic catalyst, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA), significantly lowered the charge potential to 3.73 V and increased the discharge potential to 2.75 V. PTMA facilitates both efficient formation and oxidation of Li2O2 through its n- and p-doping ability coupled with superior catalytic activity. Furthermore, PTMA effectively coats the surface of the carbon electrodes, which suppresses side-reactions between carbon and the electrolyte leading to enhanced lifetimes. Figure 1

A Bifunctional Organic Redox Catalyst for Rechargeable Lithium-Oxygen Batteries with Enhanced Performances.

An organic bifunctional catalyst poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) has been prepared and coated on carbon surface during electrode preparation. The PTMA has been applied as an efficient bifunctional catalyst for lithium-oxygen batteries with lower overpotentials, enhanced rate performances, and prolonged cycle life.

ChemInform Abstract: Catalytic Asymmetric Peroxidation of α,β‐Unsaturated Nitroalkenes by a Bifunctional Organic Catalyst.

AbstractThe first catalytic highly enantioselective peroxidation of nitroalkenes using a bifunctional cinchona sulfonamide as the catalyst is presented.

Chiral ammonium betaine-catalyzed highly stereoselective aza-henry reaction of α-aryl nitromethanes with aromatic N-Boc imines.

A highly stereoselective aza-Henry reaction of α-aryl nitromethanes with aromatic N-Boc imines was established by using C1 -symmetric chiral ammonium betaine as a bifunctional organic base catalyst. Various substituted aryl groups for both imines and nitromethanes were tolerated in the reaction, and a series of precursors for the synthesis of unsymmetrical anti-1,2-diaryl ethylenediamines was provided.

Bifunctional organic polymeric catalysts with a tunable acid-base distance and framework flexibility.

Acid-base bifunctional organic polymeric catalysts were synthesized with tunable structures. we demonstrated two synthesis approaches for structural fine-tune. In the first case, the framework flexibility was tuned by changing the ratio of rigid blocks to flexible blocks within the polymer framework. In the second case, we precisely adjusted the acid-base distance by distributing basic monomers to be adjacent to acidic monomers, and by changing the chain length of acidic monomers. In a standard test reaction for the aldol condensation of 4-nitrobenzaldehyde with acetone, the catalysts showed good reusability upon recycling and maintained relatively high conversion percentage.

Catalytic asymmetric peroxidation of α,β-unsaturated nitroalkenes by a bifunctional organic catalyst.

A new enantioselective peroxidation of α,β-unsaturated nitroalkenes was realized with an easily accessible acid–base bifunctional organic catalyst derived from cinchona alkaloids. This reaction provides unprecedented easy access to optically active chiral peroxides, as illustrated by the asymmetric synthesis of β-peroxy nitro compounds.

Chiral phosphine-squaramides as enantioselective catalysts for the intramolecular Morita–Baylis–Hillman reaction

Novel squaramides containing tertiary phosphine were developed as chiral bifunctional organic catalysts to promote the asymmetric intramolecular Morita-Baylis-Hillman reaction of ω-formyl-enones. The adducts were obtained in high yields with good-to-excellent enantioselectivity (up to 93% ee).

A recyclable bifunctional acid–base organocatalyst with ionic liquid character. The role of site separation and spatial configuration on different condensation reactions

A series of bifunctional organic catalysts containing acid and basic sites with ionic liquid characteristics have been prepared and their catalytic activity and reaction coordinate for aldol and Knoevenagel condensations have been compared. While the only factor controlling catalyst activity for the Knoevenagel condensation was the distance between the acid and base sites, the spatial orientation of the organocatalyst is also key to achieve high activity and selectivity in the Claisen-Schmidt condensation. Mechanistic studies based on theoretical DFT calculations show that the acid-base bifunctional organocatalyst follows a mechanism inspired in natural aldolases for the synthesis of trans-chalcones, being able to produce a large variety of these compounds of industrial interest. The combination of the acid-base pairs within the proper geometry and the ionic liquid nature makes this catalyst active, selective and recyclable.

Chiral primary amine mediated conjugate addition of branched aldehydes to vinyl sulfone: asymmetric generation of quaternary carbon centers

Novel L-threonine-derived bifunctional organic catalysts containing primary amine and sulfonamide groups were utilized to promote asymmetric conjugate addition of alpha,alpha-disubstituted aldehydes to 1,1-bis(benzenesulfonyl)ethylene. The adducts with quaternary stereogenic centers adjacent to an aldehyde group were obtained in high yield and with good enantioselectivity.

ChemInform Abstract: Synthesis of Aminoboronic Acids and Their Applications in Bifunctional Catalysis

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantioselective catalytic addition of nitroesters to N-carboalkyloxy imines: a route to quaternary stereocenters

A readily available, low cost bifunctional organic catalyst promoted the addition of nitroesters to imines; in the reaction between 2-nitropropionates and N-Boc protected aldehyde-imines the product bearing a new quaternary stereocenter was obtained in up to 81% ee. The positively charged catalyst was postulated to control the attack of the enolic form of nitroester to imine through a hydrogen bonding network.

Synthesis of Aminoboronic Acids and Their Applications in Bifunctional Catalysis

Amino acids have been known to catalyze organic reactions for many years, but their boronic acid counterparts are much less well-studied. Although there are a number of useful general approaches to the synthesis of protected aminoboronic acids, many practical challenges remain in the isolation and purification of free aminoboronic acids. Despite these issues, now several different chiral and achiral aminoboronic acids show promise as bifunctional organic catalysts. In this Account, we describe both advances in the synthesis of these aminoboronic acids and some of their underdeveloped potential in catalysis. The first aminoboronic acids that demonstrated catalytic properties, such as 8-quinoline boronic acid, enabled the hydrolysis and etherification of chlorohydrins. More recently, aminoboronic acids have effectively catalyzed direct amide formation. In addition, these catalysts can enable the kinetic resolution of racemic amines during the acylation process. Aminoboronic acids can also function as aldol catalysts, acting through in situ boronate enolate formation in water, and have facilitated tunable asymmetric aldol reactions, acting through the formation of an enamine. On the basis of these examples, we expect that these molecules can catalyze an even wider range of reactions. We anticipate many further discoveries in this area.

ChemInform Abstract: Asymmetric Aza‐Michael Reactions of α,β‐Unsaturated Ketones with Bifunctional Organic Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Chiral Ammonium Betaines: A Bifunctional Organic Base Catalyst for Asymmetric Mannich‐Type Reaction of α‐Nitrocarboxylates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic enantioselective conjugate additions with α,β-unsaturated sulfones

We describe the development of a highly efficient catalytic asymmetric conjugate addition to α,β-unsaturated sulfones. Utilizing practical bifunctional organic catalysts and involving air- and moisture-tolerant conditions, conjugate additions of a wide range of Michael donors to α,β-unsaturated sulfones proceeded in excellent enantioselectivity/diastereoselectivity and high yield. This efficient and operationally simple new catalytic asymmetric reaction should provide a versatile approach for the asymmetric synthesis of chiral sulfones bearing all-carbon quaternary stereocenters.