A simple and efficient automatable one step synthesis of triazolopyridines from carboxylic acids

Triazolopyridines can be rapidly and efficiently synthesized from a variety of carboxylic acids with 2-hydrazinopyridines in one simple step. The use of commercially available PS-PPh₃ resin combined with microwave heating delivered the product triazolopyridines in good yields and purities.     

A simple and efficient synthesis of 2-aryl-substituted benzimidazoles

Sodium hydrogen sulfite was used to promote condensation of o-phenylenediamine with aromatic aldehydes in dimethylformamide to obtain the corresponding 2-arylbenzimidazoles. The procedure is simple and convenient, and it implies inexpensive promoter and is characterized by short reaction time and easy purification of the final products. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 872–874. The text was submitted by the authors in English.     

Microwave-assisted one step high-throughput synthesis of benzimidazoles

One-pot synthesis of benzimidazoles from diamines and carboxylic acids was developed under microwave irradiation condition, which provided a practical and efficient method for high-throughput synthesis of this important class of heterocyclic compounds.     

A mild and efficient one pot synthesis of 1,3,4-oxadiazoles from carboxylic acids and acyl hydrazides

A convenient one pot method for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from acids and acyl hydrazides is reported. Acid activation with CDI, followed by coupling with the desired acylhydrazide and dehydration in the same pot with Ph₃P and CBr₄ affords the corresponding 1,3,4-oxadiazoles in good yield. The scope of the acid and acylhydrazide components is presented.     

A simple and efficient method of preparing α-bromo carboxylic acids

A new and convenient method for α-bromination of aliphatic carboxylic acids is reported. Heating carboxylic acids for 16 hours at 85 °C in trifluoroacetic acid with 1.5 equivalents of N-bromosuccinimide and a catalytic amount of concentrated H₂SO₄ leads to good yields of the respective α-bromocarboxylic acids.     

A simple and efficient one step synthesis of 1,3,4-oxadiazoles utilizing polymer-supported reagents and microwave heating

1,3,4-Oxadiazoles can be rapidly and efficiently synthesized from a variety of carboxylic acids and acid hydrazides in one simple step. The use of commercially available PS-PPh₃ resin combined with microwave heating delivered the product 1,3,4-oxadiazoles in high yields and purities.     

Accelerated microdroplet synthesis of benzimidazoles by nucleophilic addition to protonated carboxylic acids

We report a metal-free novel route for the accelerated synthesis of benzimidazole and its derivatives in the ambient atmosphere. The synthetic procedure involves 1,2-aromatic diamines and alkyl or aryl carboxylic acids reacting in electrostatically charged microdroplets generated using a nano-electrospray (nESI) ion source. The reactions are accelerated by orders of magnitude in comparison to the bulk. No other acid, base or catalyst is used. Online analysis of the microdroplet accelerated reaction products is performed by mass spectrometry. We provide evidence for an acid catalyzed reaction mechanism based on identification of the intermediate arylamides. Their dehydration to give benzimidazoles occurs in a subsequent thermally enhanced step. It is suggested that the extraordinary acidity at the droplet surface allows the carboxylic acid to function as a C-centered electrophile. Comparisons of this methodology with data from thin film and bulk synthesis lead to the proposal of three key steps in the reaction: (i) formation of an unusual reagent (protonated carboxylic acid) because of the extraordinary conditions at the droplet interface, (ii) accelerated bimolecular reaction because of limited solvation at the interface and (iii) thermally assisted elimination of water. Eleven examples are shown as evidence of the scope of this chemistry. The accelerated synthesis has been scaled-up to establish the substituent-dependence and to isolate products for NMR characterization.

We report a metal-free novel route for the accelerated synthesis of benzimidazole and its derivatives in the ambient atmosphere.     

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).     

One pot direct synthesis of oxazolines, benzoxazoles, and oxadiazoles from carboxylic acids using the Deoxo-Fluor reagent

A one-pot, high yield direct synthesis of various 2-substituted oxazolines, benzoxazoles, and 2-oxadiazoles from carboxylic acids using Deoxo-Fluor reagent is described.     

A simple and efficient procedure for the synthesis of benzimidazoles using air as the oxidant

Direct one-step synthesis of various benzimidazoles from phenylenediamines and aldehydes is described using air as the oxidant. The salient features of this method include a simple procedure, mild conditions, no coupling agents or commercial oxidants/additives used, no waste produced (only by-product being water), easy purification, and high generality.     

A simple, efficient Pd-catalyzed synthesis of N-sulfonylimines from organoboronic acids and tosylbenzimidoyl chlorides

A simple and efficient synthesis of N-sulfonyl ketimines through a Pd-catalyzed cross-coupling reaction between organoboronic acids and tosylbenzimidoyl chlorides under mild conditions has been developed.     

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.     

Cobalt-catalyzed intramolecular C-N and C-O cross-coupling reactions: synthesis of benzimidazoles and benzoxazoles

Cobalt(ii)-complex catalyzes efficiently the intramolecular C-N and C-O cross-couplings of Z-N'-(2-halophenyl)-N-phenylamidines and N-(2-bromophenyl)benzamides to afford the corresponding substituted benzimidazoles and benzoxazoles in the presence of K(2)CO(3) at moderate temperature. The protocol is general, air stable and affords the products selectively in moderate to high yield.     

羧酸直接酰胺化的一个新方法

N, N-二甲基取代酰胺可以方便地由脂肪族或芳香羧酸与四(二甲氨基)硅烷在无水溶剂中反应制得。     

A simple one step synthesis of new 3,5-disubstituted-4-amino-1,2,4-triazoles

A number of symmetrically 3,5-disubstituted 4-amino-1,2,4-triazoles have been prepared by the reaction of aromatic nitriles with hydrazine dihydrochloride or sulfate with an excess of hydrazine hydrate in ethyl ene or diethylene glycol under a nitrogen atmosphere. The structures of the new triazoles derivatives were confirmed by analytical and spectral data.     

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.     

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

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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.     

A novel system for the synthesis of nitriles from carboxylic acids

A simple, mild and high yielding method for the conversion of various carboxylic acids to nitriles has been developed using diphosphorus tetraiodide in combination with ammonium carbonate at room temperature.