Liquid-phase synthesis of 2-substituted benzimidazoles, benzoxazoles and benzothiazoles

A novel acid fluoride for use in the liquid-phase synthesis of substituted benzimidazoles, benzoxazoles and benzothiazoles was developed. Its synthetic utility is exemplified by a structurally diverse set of aromatic heterocycles. Final cleavage is achieved by treatment with sodium methoxide in methanol for 12 h. The corresponding benzimidazoles, benzoxazoles and benzothiazoles were obtained in good isolated yields (22-62%, four steps).     

Organocatalytic oxidative synthesis of C2-functionalized benzoxazoles,naphthoxazoles, benzothiazoles and benzimidazoles

1. Download high-res image (132KB)
2. Download full-size image

     

Voltammetric behaviour of heterocyclic systems. Pyridyl-substituted benzimidazoles,benzoxazoles and benzothiazoles

The voltammetric properties, measured at a dropping mercury electrode, have been studied for a series of 18 pyridyl-substituted heterocyclic bases [benzimidazoles, benzoxazoles and benzothiazoles]. The corresponding quarternary salts, obtained by reaction with methyl iodide, were also studied. The reduction potential was found to be dependent on the nature of the benzimidazole, benzoxazole or benzothiazole moiety and on its position on the pyridine ring as well as on the presence of a positive charge. The reversibility of the voltammetric waves was found to be function of the system structure. The effects of proton donors on the voltammetric behaviour of the bases was also investigated.     

Solid-phase combinatorial synthesis of benzothiazoles, benzimidazoles, and benzoxazoles using a traceless linker

New methodology for the solid-phase synthesis of benzothiazoles, benzimidazoles, and benzoxazoles has been developed by using a traceless 4-alkoxy-aniline linker. The desired products were released from the polymer support by imine-exchange process coupled with air oxidation. Combinatorial library consisting of 36 members has been synthesized using this linker. The yields are low to good, which highly depend on the building blocks. Recycling of the polymer support was also investigated.     

Synthesis of 2-pyranosyl benzothiazoles, benzimidazoles and benzoxazoles via nucleophilic addition reactions of pyranosyl nitrile oxides

Reaction of per-O-acetylated-β-d-pyranosyl nitrile oxides, generated by dehydrochlorination of the corresponding hydroximoyl chlorides, with 2-aminothiophenol afforded 2-(β-d-pyranosyl)benzothiazoles. 1,2-Diaminobenzene and 2-aminophenol reacted similarly to yield 2-(β-d-pyranosyl)benzimidazoles and 2-(β-d-pyranosyl)benzoxazoles, respectively. The structures of 2-β-d-glucopyranosylbenzimidazole (17), 2-(2,3,4-tri-O-acetyl-β-d-xylopyranosyl)benzimidazole (19) and the xylopyranosyl thiohydroximate 13 were established by X-ray crystallography.     

含分子内配位键的(MeOCH~2CH~2C~5H~4)~2UCl~2的合成及表征

四氯化铀与 二当量甲氧乙基环戊二烯基钠在THF中于60℃反应, 合成得到新的二(甲氧乙基环戊二烯基)二氯化铀配合物. 产物经红外光谱, ^1H NMR和质谱鉴定 .     

CuO nano-particles supported on silica,a new catalyst for facile synthesis of benzimidazoles,benzothiazoles and benzoxazoles

A facile synthetic route for benzimidazoles, benzothiazoles and benzoxazoles comprising the reaction of corresponding o-phenylenediamine, o-aminothiophenol and o-aminophenol with various aldehydes using silica supported nano-copper (II) oxide as a catalyst has been described. The catalyst exhibited a clean reaction profile with excellent yields in a short reaction time. The catalyst can be recycled effectively after use.     

An efficient and reusable heterogeneous catalyst Animal Bone Meal for facile synthesis of benzimidazoles, benzoxazoles, and benzothiazoles

A library of benzimidazoles, benzoxazoles, and benzothiazoles was efficiently synthesized by condensation of o-phenylenediamine, o-aminophenol, and o-aminothiophenol respectively with aromatic aldehydes in the presence of catalytic amounts of Animal Bone Meal (ABM) and Lewis acids doped ABMs. Reactions were conducted under reflux conditions in air. The remarkable features of this new protocol are high conversion, short reaction times, and cleaner reaction profiles, straightforward procedure, and reduction in catalyst toxicity.     

Indion 190 resin: efficient,environmentally friendly,and reusable catalyst for synthesis of benzimidazoles,benzoxazoles, and benzothiazoles

Abstract

An efficient and mild protocol has been developed for the preparation of benzimidazoles, benzoxazoles, and benzothiazoles from reactions of aldehydes with o-substituted aminoaromatics in the presence of catalytic amount of Indion 190 resin. Short reaction time, ambient conditions, simple work-up procedure, high yield, easy availability, reusability, and use of an eco-friendly catalyst are some of the striking features of the present protocol.     

Imidazolium chloride-catalyzed synthesis of benzimidazoles and 2-substituted benzimidazoles from o-phenylenediamines and DMF derivatives

A facile, general, and economical synthesis of diversely functionalized benzimidazoles and 2-substituted benzimidazoles has been realized via the imidazolium chloride-catalyzed cyclization of o-phenylenediamines with DMF derivatives. This protocol shows a broad substrate scope for aliphatic, aromatic, and heteroaromatic amides. A series of benzimidazoles and 2-substituted benzimidazoles have been obtained in moderate to excellent yields.     

Hybrid crystal NH3(CH2)4NH3SiF6 as an efficient catalyst for the synthesis of benzoxazoles,benzimidazoles and benzothiazoles under solvent-free conditions

An easy synthetic protocol for the synthesis of biologically active benzimidazole, benzothiazole and benzoxazole derivatives has been demonstrated using a hybrid crystal NH₃(CH₂)₄NH₃SiF₆ as a mild and efficient heterogeneous catalyst. Short reaction times, solvent-free conditions, good to excellent yields, easy reusability and use of an eco-friendly catalyst are some of the significant attributes of the present method.     

Syntheses and Crystal Structures of Benzyltin（Ⅳ） Derivatives of 2-Mercaptobenzothiazole

Introduction Metal thiolato complexes have been extensively investigated because of their ability to adopt various nuclearities and their relevance in biological science, since they form the inorganic part of the biologically active centers of some metalloproteins and enzymes.1-3 Recently, attention has been paid to the coordination chemistry of heterocyclic thiol/thione donors, which can give potential access to new compounds with unusual structures and reactivities,4 such as 2-mercaptobenzo-…     

The relationship between intramolecular hydrogen bonds and certain physical properties of regioselectively substituted cellulose derivatives

This article tries to provide some direct evidence about the relationship between the intramolecular hydrogen bonds in cellulose and their corresponding effect on physical properties. The formation of intramolecular hydrogen bonds has been proved to contribute directly to certain physical properties of cellulose, such as its solubility in solvents having different polarities, the relative reactivities of the hydroxyls in a repeating unit and its crystallinity, using a 6-O-methylcellulose (6MC) film that was known¹ to have intramolecular hydrogen bonds. The excellent solubility of 6MC when compared with other cellulose derivatives indicated a lack of interchain hydrogen bonds. A comparison of the relative reactivities between the C-2 and C-3 position hydroxyls in 6MC also indicates that intramolecular hydrogen bonds once formed in 6MC films are possibly maintained even after dissolution in solvents. In addition, the poor crystallinity exhibited by 6MC supports the idea that crystallization in cellulosics may be dependent more upon preferencial interchain hydrogen bonding at the C-6 position hydroxyls than upon a uniform structure such as that found in 6MC, where every structural unit is completely and regioselectively substituted, distinguishing it from other synthetic polymers such as polyolefins and polyesters. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 717–723, 1997     

Crystal structures and hydrogen bonding schemes in four benzamide derivatives (2-hydroxy-benzamide, 2-hydroxy-thiobenzamide, 2-hydroxy-N,N-dimethyl-benzamide,and 2-Hydroxy-N,N-dimethyl-thiobenzamide)

Summary 2-Hydroxy-benzamide, C₇H₇NO₂; monoclinic; I2/a-C _2h ⁶ ;a=12.901 (2),b=4.982 (1),c=20.987 (3) Å; =91.50 (2)°;Z=8. 2-Hydroxy-thiobenzamide, C₇H₇NOS; monoclinic; P2₁/n-C _2h ⁵ ;a=13.508 (5),b=6.780 (2),c=15.878 (6) Å; =93.74 (5)°;Z=8. 2-Hydroxy-N,N-dimethyl-benzamide, C₉H₁₁NO₂; orthorhombic; Pbca-D _2h ¹⁵ ;a=11.752 (2),b=16.680 (3),c=9.079 (2) Å;Z=8. 2-Hydroxy-N,N-dimethyl-thiobenzamide, C₉H₁₁NOS; monoclinic; P2₁/c-C _2h ⁵ ;a=6.983 (1),b=11.652 (3),c=11.704 (3) Å; =100.02 (2)°;Z=4. The crystal structures of these four compounds were determined (respectively refined: 2-hydroxy-benzamide) by single crystal X-ray data. The refinements of the structure parameters by least squares methods yielded in all casesR<0.056. The hydrogen atoms were located by means of difference Fourier summations. The O-H ... O distances are 2.513 (1) Å in 2-hydroxy-benzamide (intramolecular) and 2.625 (1) Å in 2-hydroxy-N,N-dimethyl-benzamide (intermolecular). The two O-H ... S distances in 2-hydroxy-thiobenzamide are 2.904 (2) Å and 2.918 (2) Å (intramolecular, two molecules in the asymmetric unit) and 3.228 (2) Å in 2-hydroxy-N,N-dimethyl-thiobenzamide (intermolecular). Clear N-H ... O hydrogen bonds with 2.926 (1) Å and 3.006 (1) Å occur only in the structure of 2-hydroxy-benzamide (intermolecular).

---

Die Kristallstrukturen und Wasserstoffbrücken-Bindungsschemata in vier Benzamid-Derivaten

Zusammenfassung 2-Hydroxy-benzamid, C₇H₇NO₂; monoklin; I2/a-C _2h ⁶ ;a=12.901 (2),b=4.982 (1),c=20.987 (3) Å; =91.50 (2)°;Z=8. 2-Hydroxy-thiobenzamid, C₇H₇NOS; monoklin; P2₁/n-C _2h ⁵ ;a=13.508 (5),b=6.780 (2),c=15.878 (6) Å; =93.74 (5)°;Z=8. 2-Hydroxy-N,N-dimethyl-benzamid, C₉H₁₁NO₂; orthorhombisch; Pbca-D _2h ¹⁵ ;a=11.752 (2),b=16.680 (3),c=9.079 (2) Å;Z=8. 2-Hydroxy-N,N-dimethyl-thiobenzamid, C₉H₁₁NOS; monoklin; P2₁/c-C _2h ⁵ ;a=6.983 (1),b=11.652 (3),c=11.704 (3) Å; =100.02 (2)°;Z=4. Die Kristallstrukturen dieser vier Verbindungen wurden mittels Röntgen-Einkristalldaten bestimmt (bzw. verfeinert: 2-Hydroxy-benzamid). Die Verfeinerungen der Strukturparameter nach der Methode der kleinsten Quadrate ergab in allen FällenR<0.056. Die Wasserstoffatome konnten anhand von Differenz-Fourier-Summationen belegt werden. Die O-H ... O-Abstände haben folgende Werte: 2.513(1)Å in 2-Hydroxy-benzamid (intramolekular) und 2.625(1) Å in 2-Hydroxy-N,N-dimethyl-benzamid (intermolekular). Die zwei O-H ... S-Abstände sind in 2-Hydroxy-thiobenzamid 2.904(2)Å und 2.918(2)Å (intramolekular, zwei moleküle in der asymmetrischen Einheit) und 3.228(2)Å in 2-Hydroxy-N,N-dimethyl-thiobenzamid(intermollekular). Klar zuzuordnende N-H ... O-Wasserstoffbrücken mit 2.926(1)Å und 3.006(1)Å treten lediglich in der Struktur des 2-Hydroxy-benzamid auf (intermolekular).

     

Reinvestigation of intramolecular hydrogen bond in malonaldehyde derivatives: An ab initio,AIM and NBO study

The RAHB systems in malonaldehyde and its derivatives at MP2/ 6‐311++G(d,p) level of theory were studied and their intramolecular hydrogen bond energies by using the related rotamers method was obtained. The topological properties of electron density distribution in O? H···O intramolecular hydrogen bond have been analyzed in term of quantum theory of atoms in molecules (QTAIM). Correlations between the H‐bond strength and topological parameters are probed. The results of QTAIM clearly showed that the linear correlation between the electron density distribution at HB critical point and RAHB ring critical point with the corresponding hydrogen bond energies was obtained. Moreover, it was found a linear correlation between the electronic potential energy density, V(r_cp), and hydrogen bond energy which can be used as a simple equation for evaluation of HB energy in complex RAHB systems. Finally, the similar linear treatment between the geometrical parameters, such as O···O or O? H distance, and Lp(O)→σ*_OH charge transfer energy with the intramolecular hydrogen bond energy is observed. © 2010 Wiley Periodicals, Inc., Int J Quantum Chem, 2011     

Efficient,Iron-Catalyzed Synthesis of 2-Mercaptobenzothiazole Through S-Arylation/Heterocyclization of 2-Haloaniline with Potassium Xanthate

A mild and practical method for the synthesis of 2-mercaptobenzothiazole has been developed by using iron as an efficient catalyst. The present tandem reaction process allows access to a wide range of 2-mercaptobenzothiazoles in good to excellent yields by the reaction of 2-haloaniline with potassium O-ethyl dithiocarbonate in the presence of FeF₃ as a catalyst and 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl as a ligand under an atmosphere of argon.     

Copper‐catalyzed highly efficient aerobic oxidative synthesis of benzimidazoles,benzoxazoles and benzothiazoles from aromatic alcohols under solvent‐free conditions in open air at room temperature

Solvent‐free oxidative synthesis of benzimidazoles, benzoxazoles and benzothiazoles from aromatic alcohols and o‐phenylenediamine, o‐aminophenol and o‐aminothiophenol has been achieved by using CuCl, 2,2′‐bipyridine and TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl). The reaction proceeds via a dehydrogenation in open air at room temperature, and a wide variety of derivatives were obtained in good to excellent yields. The reaction mechanism was proposed and this method provides a mild and efficient access to substituted benzimidazoles, benzoxazoles and benzothiazoles. Copyright © 2013 John Wiley & Sons, Ltd.