Cellulose Sulfuric Acid Catalyzed One-Pot Three-Component Synthesis of Imidazoazines

Abstract

Imidazoazines have been synthesized by a one-pot three-component condensation reaction of an aldehyde, a 2-aminoazine and an isocyanide in the presence of the cellulose sulfuric acid, as an effective bio-supported catalyst in excellent yields. The reaction work-up is simple and the catalyst can be easily separated from the product and reused in several times.Key words cellulose sulfuric acid; bio-supported catalyst; imidazo[1,2-a]pyridine; isocyanide; multi-component reaction Imidazo[1,2-a]pyridines, as an important class of versatile pharmaceutically and biologically active compounds spanning applications in anti-inflammatory 1,2) and antibacterial agents, 3) inhibitors of gastric acids secretion, 4) calcium channel blockers, 5) and antiulcer based therapies. 6) As a result, numerous two-and three-component approaches for their synthesis have been reported. [7][8][9][10][11][12][13][14] Biopolymers, especially cellulose and its derivatives, 15) have some unique properties, which make them attractive alternatives for conventional organic or inorganic supports for catalytic applications. Among others, they are extremely inert, inexpensive, biodegradable and environmentally benign allowing various reaction conditions to be employed. Cellulose is the most abundant natural material in the world and it has been widely studied during the past decades because it is a biodegradable material and a renewable resource.In recent years, the emphasis of science and technology is shifting more towards environmentally friendly and sustainable resources and processes; in this regard, biopolymers are attractive candidates to explore for supported catalysis. 16,17) Several interesting biopolymers for example alginate, 18) gelatin, 19,20) starch 21) and chistosan 22) derivatives have been utilized as a support for catalytic applications.During the course of our studies on the development of new routes for the synthesis of organic compounds using solid acid catalysts in organic transformations [23][24][25][26][27] and our interest in isocyanide-based MCRs, [28][29][30][31] we developed the synthesis of imidazoazines 4a-j via the three-component condensation of an aldehyde 1, a 2-aminoazine 2 and an isocyanide 3 in the presence of catalytic amount of cellulose sulfuric acid at room temperature (Chart 1). ExperimentalApparatus Melting points were measured on an Electrothermal 9100 apparatus and are uncorrected. The elemental analyses were performed with an Elementar Analysensysteme GmbH VarioEL. Mass spectra were recorded on a FINNIGAN-MAT 8430 mass spectrometer operating at an ionization potential of 70 eV. IR spectra were recorded on a Shimadzu IR-470 spectrometer.1 H-and 13 C-NMR spectra were recorded on a BRUKER DRX-300 AVANCE spectrometer at 300.13 and 75.47 MHz, respectively. All the products (except 4g) are known compounds, which were identified by IR and 1 H-NMR spectral data and comparing their melting points with literature reports.Preparation of Cellulose Sulfuric Acid To a magnetically stirred mixture of 5.00 g of cellulos...

Green Synthesis, Characterization and Antidiabetic Activity of 2-Substituted Aryl/Alkyl-N-Aryl/Alkyl Imidazo[1,2-a]pyridin-3-amine Derivatives

“…To the best of our knowledge, the synthesis of compounds 6f, 7b, 7c, 7e-7f are new and have not been reported in the literature so far. Apart from the above mentioned reagents, in general imidazo [1,2-a]pyridines have been reported to be synthesized by different methodologies for this type of condensation reactions such as Sc(OTf)3 [38], ZnCl2 [39], MgCl2 [40], ZrCl4 [41], SnCl2·2H2O [42], HClO4 [27], AcOH [28], p-TSA [43], montmorillonite K-10 [44], cellulose sulfuric acid [26], catalyst free and solvent free reaction condi-tions [45,46]. Most of these methods have many limitations in terms of lower product yields, toxicity, longer reaction time, higher energetic reaction conditions or use of hazardous and volatile organic solvents like acetonitrile, toluene, chloroform etc.…”

One‐pot Synthesis of 3‐Aminoimidazo[1,2‐a]pyridines Catalyzed by Heteropolyacids

“…As it can be seen, these heteropolyacids are more effective than other catalysts, 7 being compared economically and environmentally attractive and effective catalysts for various reactions and having high capability in practical uses. 23 The efficiency of various heteropolyacids has also been compared ( …”

“…6 As a result, numerous two-and three-component approaches for their synthesis have been reported. [7][8][9][10][11][12][13][14] The amino group at position 2 confers special properties to this nucleus, which has been used to prepare 2-aminoimidazo[1,2-a]pyridines as anti-rhinovirus agents. 15 …”

Cellulose sulfuric acid (CSA) and starch sulfuric acid (SSA) as solid and heterogeneous catalysts in green organic synthesis: recent advances

“…In addition, EMF could be also synthesized in good yield (72.5%) directly from the fructose through one-pot reaction, which included that the dehydration of fructose into HMF, followed by etherification of HMF into EMF. Shaabani and co-workers 44 have also developed a high yielding synthesis of imidazoazine derivatives through the one-pot three-component condensation reaction of aldehydes, 2-aminoazine and isocyanides in the presence of catalytic amount of cellulose sulfuric acid (CSA), as an effective bio-supported catalyst in methanol at room temperature (Scheme 15). The results showed that the efficiency and the yield of the product in methanol were higher than those obtained in other solvents like water, ethanol, dichloromethane, toluene, acetonitrile and solventfree condition.…”