Lithium bromide as an efficient,green, and inexpensive catalyst for the synthesis of quinoxaline derivatives at room temperature

Abstract

An efficient, simple, and green procedure for the synthesis of quinoxaline derivatives is described. The condensation of 1,2-diamines with 1,2-diketones using lithium bromide (LiBr) in H₂O/EtOH as a green reaction media at room temperature affords the title compounds in high to excellent yields and in short reaction times.     

Keggin type heteropolyacids-catalyzed synthesis of quinoxaline derivatives in water

Keggin type heteropolyacids was found to be an efficient and reusable catalyst for the synthesis of biologically active quinoxaline derivatives from the condensation of 1,2-diamine with 1,2-dicarbonyl compounds in excellent yields in water.This method provides a new and efficient protocol in terms of small quantity of catalyst,a wide scope of substrates,and simple work-up procedure.     

A one-pot synthesis of 1,2,4,5-tetraarylimidazoles using molecular iodine as an efficient catalyst

Molecular iodine is a cheap, nontoxic catalyst, which acts as an efficient catalyst for the synthesis of 1,2,4,5-tetraarylimidazoles using benzoin, an aromatic aldehyde and an amine in the presence of ammonium acetate. The advantage of this method is the direct use of benzoin, which is transformed into benzil in situ and condenses further to generate the imidazole in a one-pot sequence.     

Chemoselective hydrolysis of tert-butyl esters in acetonitrile using molecular iodine as a mild and efficient catalyst

A simple, mild and efficient method for the hydrolysis of tert-butyl esters using molecular iodine as a catalyst is described. Acid labile protecting groups, such as N-Boc, OBn, OAc and double bonds, are compatible under the reaction conditions.     

Amberlyst-15: an efficient and reusable catalyst for multi-component synthesis of 3,4-dihydroquinoxalin-2-amine derivatives at room temperature

We demonstrate on the synthesis of multifunctional 3,4-dihydroquinoxalin-2-amine derivatives through a three-component condensation of substituted o-phenylenediamines (OPDA), diverse ketones, and various isocyanides in the presence of an efficient and reusable amberlyst-15 catalyst which was found to be highly active and afforded excellent yields (85-99%) in ethanol at room temperature (2-3 h).     

Pentafluorophenylammonium triflate: A highly efficient catalyst for the synthesis of quinoxaline derivatives in water

A simple, inexpensive, environmentally friendly and efficient route for the rapid and efficient synthesis of quinoxaline derivatives using pentafluorophenylammonium triflate (PFPAT) as a catalyst is described. Various quinoxaline derivatives were synthesized in good to excellent yields. The preparation of PFPAT catalyst from simple and readily available starting materials makes this method more affordable.     

Molecular iodine: a powerful catalyst for the easy and efficient synthesis of quinoxalines

Various biologically important quinoxaline derivatives were efficiently synthesized in excellent yields using inexpensive, nontoxic, and readily available bench top chemical, iodine in catalytic amount (10 mol %). Besides this, a systematic study was carried out to evaluate parameters such as solvent and catalyst loading. Several aromatic as well as aliphatic 1,2-diketones and aromatic 1,2-diamines, such as substituted phenylene diamines, tetra amines were further subjected to condensation using catalytic amounts of iodine to afford the products in excellent yield.     

Efficient protocol for the synthesis of quinoxaline, benzoxazole and benzimidazole derivatives using glycerol as green solvent

A straightforward, efficient and more sustainable catalyst-free method has been developed for the synthesis of quinoxaline, benzoxazole, and benzimidazole ring system in glycerol to achieve yields that were comparable to or better than, those in conventional media. It is noteworthy that the reaction was exclusively carried out in glycerol-water system, rendering the methodology highly valuable from both environment and economic points of view.     

Citric acid:An efficient and green catalyst for rapid one pot synthesis of quinoxaline derivatives at room temperature

The condensation of o-phenylenediamines with 1,2-dicarbonyl compounds in the presence of citric acid afforded the corresponding quinoxaline derivatives in higher yields at room temperature in ethanol,and most of the reactions were completed in less than 1 min.     

A recyclable and highly effective sulfated TiO2-P25 for the synthesis of quinoxaline and dipyridophenazine derivatives at room temperature

Sulfated TiO₂-P25 has been prepared using H₂SO₄ and used for the synthesis of quinoxaline and dipyridophenazine derivatives. Sulfate loading by H₂SO₄ increases the Lewis acidity of TiO₂-P25. This catalyst gives excellent yield with less reaction time and it is an inexpensive, easily recyclable catalyst for this reaction.     

Chemoselective hydrolysis of terminal isopropylidene acetals in acetonitrile using molecular iodine as a mild and efficient catalyst

A simple, mild and efficient method for deprotection of acetonides in the presence of molecular iodine is described. Acid labile protecting groups such as PMB, OMe, OBn, allyl and propargyl are compatible with the reaction conditions, while TBS, TBDPS, TMS and THP ethers were unstable under the same conditions.     

甘油作为相转移催化剂催化合成喹喔啉类化合物

本文以绿色介质水为溶剂,甘油作为相转移催化剂,通过1,2-二羰基化合物和1,2-二胺类化合物缩合合成一系列喹喔啉类化合物。甘油作为生物柴油工业的主要副产品,无毒无害,可生物降解,有机合成中的应用为其找到了很好的应用前景。     

A one-pot three-component reactions for the synthesis of fully substituted spiro indeno[1,2-b]quinoxaline derivatives

An efficient and simple approach of the synthesis of some spiro indeno[1,2-b]quinoxalines via a one-pot three-component reaction of 11H-indeno[1,2-b]quinoxalin-11-one, pyrazolone, and malononitrile in the presence of Na₂CO₃ at 70 °C is reported. This reaction has shown to have high atom economy.     

Regioselective synthesis of pyrano[3,2-f]quinoline and phenanthroline derivatives using molecular iodine

A series of polysubstituted pyrano[3,2-f]quinoline and phenanthroline derivatives have been synthesized by molecular iodine-catalyzed tandem reaction of various propargylic alcohols with or without substituted amines in excellent yields. Moreover, the cyclized side products are also pyrano[3,2-f]quinoline and phenanthroline derivatives.     

Room temperature synthesis of benzimidazole derivatives using reusable cobalt hydroxide (II) and cobalt oxide (II) as efficient solid catalysts

Here we demonstrate the synthesis of benzimidazoles through the coupling of 1,2-phenylenediamine with aldehydes by using Co(OH)₂ and similarly CoO(II) as efficient solid catalysts in ethanol at room temperature. The Co(OH)₂ solid catalyst gave better yields (82-98%) in short reaction times (4-7 h) than CoO(II) catalyst (80-94%, 6-9 h). These commercially available cheap catalysts are more active than many reported expensive heterogeneous catalysts.     

An Efficient and Facile Synthesis of Quinoxaline Derivatives Catalyzed by KHSO4 at Room Temperature

Summary. A facile synthesis of quinoxaline derivatives catalyzed by KHSO₄ in very high yields at room temperature is reported.     

Ketones as a new synthon for quinoxaline synthesis

o-Phenylenediamines react with an array of ketones in PEG-400 at 60 °C under an atmosphere of air in the presence of KOH to afford the corresponding quinoxalines in good yields.     

An efficient synthesis of novel heterocycle-fused derivatives of 1-oxo-1,2,3,4-tetrahydropyrazine using Ugi condensation

We present a convenient synthesis of novel pyrrole- and indole-fused 1-oxo-1,2,3,4-tetrahydropyrazine heterocyclic structures using a novel modification of four-component Ugi condensation. We demonstrate the usefulness and versatility of the developed approach for the synthesis of variously substituted compounds, and discuss the scope and limitations of the chemistry involved.     

A facile electrochemical method for the synthesis of phenazine derivatives via an ECECC pathway

Electrochemical oxidation of 2,3-dimethylhydroquinone 1 has been studied in the presence of o-phenylenediamines 3a-c as nucleophiles in aqueous solution, using cyclic voltammetry and controlled potential coulometry. The results indicate that the quinone 2 derived from 2,3-dimethylhydroquinone participates in Michael addition and imine condensation reactions with o-phenylenediamine via an ECECC mechanism, and is converted to the corresponding phenazine derivatives 7a-c and 7′b. The electrochemical synthesis of compounds 7a-c and 7′b has been performed successfully at a carbon rod electrode in an undivided cell with good yields and high purities.