O-substituted Anilines Research Articles

Cobalt isatin-Schiff-base derivative of MOF as a heterogeneous multifunctional bio-photocatalyst for sunlight-induced tandem air oxidation condensation process

A sunlight-induced tandem air oxidation-condensation of alcohols with ortho-substituted anilines or malononitrile for the efficient synthesis of benz-imidazoles/-oxazoles/-thiazoles, or benzylidene malononitrile catalyzed by Co-isatin-Schiff-base-MIL-101(Fe) as a heterogeneous multifunctional bio-photocatalyst is reported. In these reactions, Co-isatin-Schiff-base-MIL-101(Fe) acts both as a photocatalyst, and a Lewis acid to catalyze the reaction of the in-situ formed aldehydes with o-substituted anilines or malononitrile. A significant decrease in the band gap energy and an increase in the characteristic emission of MIL-101(Fe) after functionalization with cobalt Schiff-base according to the DRS analysis and fluorescence spectrophotometry, respectively, indicate that the photocatalytic effectiveness of the catalyst is associated primarily to the synergetic influence of Fe–O cluster and Co-Schiff-base. EPR results obviously pointed out that Co-isatin-Schiff-base-MIL-101(Fe) is capable of creating 1O2 and O2⋅− as active oxygen species under visible light irradiation. Using an inexpensive catalyst, sunlight irradiation, air as a cost-effective and abundant oxidant, and a low amount of the catalyst with recoverability and durability in ethanol as a green solvent, make this methodology as an environmentally friendly process with energy-saving organic synthetic strategies. Furthermore, Co-isatin-Schiff-base-MIL-101(Fe) displays excellent photocatalytic antibacterial activity under sunlight irradiation against E. coli, S. aureus and S. pyogenes. Based on our knowledge, this is the first report of using a bio-photocatalyst for the synthesis of the target molecules.

Microwave-assisted hydrogen peroxide-mediated synthesis of benzoxazoles and related heterocycles via cyclodesulfurization

A novel approach has been developed to construct benzoxazoles and similar N- and S-containing heterocycles from their corresponding isothiocyanates and o-substituted anilines via cyclodesulfurization. The reaction was found to proceed via in situ formation of disubstituted thiourea, followed by intramolecular cyclodesulfurization to yield the desired benzazole. Cyclodesulfurization was achieved by the application of safer and inexpensive oxidant, hydrogen peroxide (H2O2) under microwave irradiation. In addition to the safe environmental footprints that hydrogen peroxide exhibits, the absence of any base or additive makes it a mild and green synthetic strategy. This method contributes to the field of metal- and base-free cyclodesulfurization, thereby aids the synthesis of pharmacologically potent heterocyclic scaffolds.

Synthesis of Benzimidazoles, Benzoxazoles and Benzothiazole by the Reaction of 2-Amino-4,5-dihydro-3-furancarbonitrile and o-Substituted Anilines in the Catalysis of Trimetylamine Hydrochloride

Synthesis of Benzimidazoles, Benzoxazoles and Benzothiazole by the Reaction of 2-Amino-4,5-dihydro-3-furancarbonitrile and o-Substituted Anilines in the Catalysis of Trimetylamine Hydrochloride

Studies on Associated Solutions: Thermodynamic Parameters of Binary Liquid Mixtures of Propiophenone and o-Substituted Anilines

The densities (ρ), speeds of sound (u), and viscosities (η) are reported for binary mixtures of propiophenone with ortho-substituted aniline (2-chloroaniline, 2-methylaniline, and 2-methoxyaniline) over the entire composition range from 303.15 to 318.15 K and at atmospheric pressure 0.1 MPa. The excess/deviation functions (VE, $$k_{s}^{E}$$ , and Δη) are calculated from the measured densities, speeds of sound and viscosities at experimental temperatures. The excess properties have been analyzed through molecular interactions. The FT-IR data indicate that the formation of intermolecular hydrogen bonding (N–H⋅⋅⋅O–H) between hydrogen atom of amine group of o-substituted aniline and oxygen atom of carbonyl of propiophenone in the binary liquid mixtures.

Visible light induced tandem reactions: An efficient one pot strategy for constructing quinazolinones using in-situ formed aldehydes under photocatalyst-free and room-temperature conditions

A facile tandem route has been developed for constructing quinazolinones from various aminobenzamides and in-situ generated aldehydes. Visible light was found to play a dual role: first oxidizes the alcohol to the aldehyde and then facilitates its cyclization with o-substituted aniline. Furthermore, alcohols are perfect alternatives to aldehydes because they are greener, more available, more economical, more stable, and less toxic than aldehydes. The first reaction step continuously provides material for the second step, which effectively reduces loss through volatilization, oxidation, and polymerization of the aldehyde, while avoiding its toxicity. A variety of quinazolinones can be prepared in the presence of visible light without any additional photocatalyst. The developed synthesis protocol proceeds with the merits of mild conditions, broad substrate scope, operational simplicity, and high atom efficiency, with an eco-energy source under metal-free, photocatalyst-free, and ambient conditions.

Straightforward synthesis of benzoxazoles and benzothiazoles via photocatalytic radical cyclization of 2-substituted anilines with aldehydes

Eosin Y-catalyzed one-pot coupling and cyclization of o-substituted anilines with aldehydes to form benzoxazoles and benzothiazoles under mild condition has been developed. The reaction scope was broadly tolerant of various 2-substituted anilines and aldehydes. The desired products were obtained in high yields with the use of eosin Y as a photocatalyst under a substantial refinement of reaction conditions in comparison with previous literature. Based on the experimental results observed, a plausible mechanism involving a radical process has been proposed.

Cyclization of o-Phenylenediamine and o-Substituted Anilines with Supercritical Carbon Dioxide

Abstract—It is demonstrated that tin(II) 2-ethylhexanoate and tin(II) oxide are effective catalysts for the reaction of cyclization of model arylamines o-NH2(C6H4)XH (X = NH, O, S, CH2NH) in supercritical carbon dioxide with the formation of benzo-1,3-azol-2-ones and 3,4-dihydroquinazolin-2-one. Optimal conditions for these reactions are found. Possible mechanisms for these processes are proposed, depending on the catalyst used.

Исследование реакции метилового эфира ароилпировиноградной кислоты с о-замещенным анилином методом ИК-фурье-спектроскопии

Исследование реакции метилового эфира ароилпировиноградной кислоты с о-замещенным анилином методом ИК-фурье-спектроскопии

Metal-Free Synthesis of N-Containing Heterocycles from o-Substituted Aniline Derivatives via 2,4,6-Trihydroxybenzoic Acid-Catalyzed Oxidative Dehydrogenation of Benzylamines under Oxygen Atmosphere

Metal-Free Synthesis of N-Containing Heterocycles from o-Substituted Aniline Derivatives via 2,4,6-Trihydroxybenzoic Acid-Catalyzed Oxidative Dehydrogenation of Benzylamines under Oxygen Atmosphere

Mesomeric effect on thermodynamic parameters of binary liquid mixtures of N-methyl formamide and o-substituted anilines

In the present investigation, the densities (ρ) and viscosities (η) are reported for binary mixtures N-methylformamide with o-substituted aniline (2-chloroaniline, 2-methylaniline and 2-methoxyaniline) over the entire composition range from 303.15 K to 318.15 K and at atmospheric pressure 0.1 MPa. The experimental data is used to calculate excess volume (VE), deviation in viscosity (∆ η) and excess Gibbs energy of activation of viscous flow (G⁎E). The excess partial molar volumes, V¯m,1E and V¯m,2E and excess partial molar volumes V¯m,1°E and V¯m,2°E at infinite dilution have also been calculated. The variations in these properties with composition for all the binary mixtures suggest loss of dipolar association, difference in size and shape of the component molecules, dipole-dipole interaction and hydrogen bonding between N-methylformamide with o-substituted aniline. Furthermore, the FTIR spectra have been recorded at 298.15 K and found to be useful for understanding the presence of hydrogen bonding between nitrogen atom of amino group of o-substituted aniline and hydrogen atom of the amide group of N-methylformamide in the liquid mixtures. A good agreement is obtained between excess quantities and spectroscopic data.

Efficient Construction of N-heterocycles from Benzylic Ethers/Alcohols and o-Substituted Anilines without Using any Catalyst and Additive

Efficient Construction of N-heterocycles from Benzylic Ethers/Alcohols and o-Substituted Anilines without Using any Catalyst and Additive

Electrochemical Synthesis of Benzazoles from Alcohols and o-Substituted Anilines with a Catalytic Amount of Co(II) Salt.

An electrochemical synthesis of benzazoles directly from alcohols and o-substituted anilines has been developed. The reaction conditions have been optimized by varying the composition of the electrolyte and the metal salt used as catalyst. The cyclization proceeds smoothly with a catalytic amount of a cobalt salt under air at room temperature to afford 2-substituted benzimidazoles, benzothiazoles, and benzoxazoles in good to excellent yields with a wide substrate scope.

Atmospheric CO2 promoted synthesis of N-containing heterocycles over B(C6F5)3 catalyst

CO2 gas greatly promoted the cyclization of various o-substituted anilines with N,N-dimethylformamide, producing N-containing heterocycles in high yields.

ChemInform Abstract: Unexpectedly Simple Synthesis of Benzazoles by tBuONa‐Catalyzed Direct Aerobic Oxidative Cyclocondensation of o‐Thio/Hydroxy/Aminoanilines with Alcohols under Air.

tBuONa-catalyzed direct aerobic oxidative cyclocondensation reactions of readily available alcohols and o-thio/hydroxy/aminoanilines under air have been developed and provide an efficient, practical, and green method for the synthesis of benzazoles. Mechanistic studies revealed that o-substituted anilines promote the initial aerobic alcohol-oxidation step, which explains the high reactivity and success of this unexpectedly simple and practical cyclocondensation method.

Unexpectedly Simple Synthesis of Benzazoles by tBuONa‐Catalyzed Direct Aerobic Oxidative Cyclocondensation of o‐Thio/Hydroxy/Aminoanilines with Alcohols under Air

tBuONa-catalyzed direct aerobic oxidative cyclocondensation reactions of readily available alcohols and o-thio/hydroxy/aminoanilines under air have been developed and provide an efficient, practical, and green method for the synthesis of benzazoles. Mechanistic studies revealed that o-substituted anilines promote the initial aerobic alcohol-oxidation step, which explains the high reactivity and success of this unexpectedly simple and practical cyclocondensation method.

Iron-catalyzed aerobic oxidative functionalization of sp3 C–H bonds: a versatile strategy for the construction of N-heterocycles

Iron-catalyzed aerobic oxidative functionalization of sp3 C–H bonds using a biofriendly iron catalyst in combination with O2 or air as the sole oxidant has been developed for the construction of N-heterocycles from easily available carboxylic acid derivatives and o-substituted anilines.

Catalytic role of ruthenium(III) complexes bearing cystamine-based disulfide ligands on the N-alkylation of o-substituted anilines

Ruthenium(III) complexes of cystamine-based disulfide ligands with the general formula [RuXL1−4] (X = Cl or Br; L1−4 = pentadentate Schiff base ligands) were synthesized from ruthenium precursor complexes [RuX3(AsPh3)3] (X = Cl or Br) and disulfide ligands derived from cystamine and 2-hydroxy-substituted aromatic aldehydes, viz., salicylaldehyde, 5-chlorosalicylaldehyde, o-vanillin, and 2-hydroxynaphthaldehyde for L1–L4, respectively. The ligands and their complexes were structurally characterized by elemental, spectral (UV–Vis, IR, NMR, EPR, and ESI-mass) and cyclic voltammetry methods. The new complexes have shown effective hydrogen transfer properties, which were studied in the catalytic transfer hydrogenation of some secondary alcohols using gas chromatography. The catalytic properties of the complexes toward the N-alkylation of o-substituted anilines were analyzed in detail showing that this catalytic reaction involved two important hydrogen transfer steps. Hence, a new suitable and efficient catalytic system has been investigated for the synthesis of various benzazoles in a one-pot reaction.

Ammonium Chloride-catalyzed Synthesis of Benzo-fused Heterocycles from o-Substituted Anilines and Orthoesters

Click to increase image sizeClick to decrease image size Acknowledgments C. F. wishes to thank Oklahoma State University for providing support in the form of a Niblack Scholarship. Funding for the 300 MHz NMR spectrometer of the Oklahoma Statewide Shared NMR facility was provided by NSF (BIR-9512269), the Oklahoma State Regents for Higher Education, the W. M. Keck Foundation, and Conco, Inc. Finally, the authors wish to thank the OSU College of Arts and Sciences for funds to upgrade our departmental FT-IR and GC-MS instruments. Chelsea Fortenberry is a 2011–2012 Niblack Undergraduate Research Scholar and Baskar Nammalwar is her mentor.

Tautomerism in Schiff bases. The cases of 2-hydroxy-1-naphthaldehyde and 1-hydroxy-2-naphthaldehyde investigated in solution and the solid state

Schiff bases derived from hydroxyl naphthaldehydes and o-substituted anilines have been prepared and their tautomerism assessed by spectroscopic, crystallographic, and computational methods. Tautomeric equilibria have also been studied and reveal in most cases a slight preference of imine tautomers in solution; a fact supported by DFT calculations in the gas phase as well as incorporating solvent effects through the SMD model. To simulate the effect exerted by the crystal lattice on tautomer stability, we have developed a computational protocol in the case of 1-tert-butyl-2-(2-hydroxy-1-naphthylmethylene)aminobenzene whose data have been obtained experimentally at 120 K. Although a rapid imine-enamine interconversion may be occurring in the solid state, the imine tautomer becomes the most stable form and the energy difference should be related to the difference in the packing of the molecules.

1,3-Dibromo-5,5-dimethylhydantoin as an efficient homogeneous catalyst for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines

A simple and highly efficient method for synthesis of benzoxazoles, benzimidazoles, and oxazolo[4,5-b]pyridines is described. Condensation of orthoesters with o-substituted anilines or 2-amino-3-hydroxypyridine was performed in the presence of catalytic amounts of commercially available, inexpensive, and moisture-stable 1,3-dibromo-5,5-dimethylhydantoin under solvent-free conditions. The corresponding heterocycles were obtained in good to excellent yields. The main advantages of the present procedure are mild reaction conditions, short reaction times, high yields of products, easy work-up, and absence of solvent.