Microwave-Assisted One-Pot Synthetic Pathways for Pyrido[2,3-d]imidazole Derivatives.

The basicities of 22 derivatives of aniline with methyl, amino, hydroxy, chloro, bromo, iodo, nitro and carboxy substituents were determined potentiometrically against a standard in nitrobenzene solvent. Methyl, amino and hydroxy substituents had a basicity-increasing effect and the others a basicity-decreasing effect on aniline. The basicity-increasing effects of each substituent differs depending on whether it is at the ortho, meta or para position. The basicity-increasing order of methyl and amino substituents is p > m > o, whereas that of the hydroxy substituent is p > o > m. Halogens, nitro and carboxy substituents all decrease the basicity of aniline. The basicity-decreasing order of the halogens is o > m > p, and moreover is in the order l > Br > Cl for para derivatives and Br > Cl for ortho and meta derivatives. The basicity-decreasing effect of a nitro substituent is in the order o > p > m, whereas that of a carboxy substituent is p > o > m. Among the isomers of ortho-and para-orienting substituents, para isomers, and among the isomers of meta-orienting substituents meta isomers are the most basic. Of the substituents, the basicity-increasing effects decrease in the order NH2 > OH > CH3 and the basicity-decreasing effects in the order NO2 > COOH > l > Br > Cl.

The photochemical and aluminium chloride-catalyzed Fries rearrangement of a series of aryl hydrogen succinates3 a–f to the corresponding 4-oxoacids1 a–f are compared. Both approaches are complementary: the photochemical process is more general and becomes the method of choice for the succinoylation of phenols supporting alkoxy or hydroxy substituents, while the classical rearrangement is superior in the presence of alkyl or halogen substituents. These results are applied to the preparation of the 2(3H)-furanones2 a–f.

Effect of the amino and hydroxy substituents on the photophysical properties of 1,4-disubstituted-9,10-anthraquinone dyes

The simple and efficient procedure for a four-component condensation of benzil, aromatic aldehydes, ammonium acetate and 8-hydroxy-7-iodoquinoline-5-sulfonic acid (HISA) as the catalyst under microwave irradiation in mild reaction conditions to synthesis some of 2,4,5-triarylsubstituted imidazole derivatives. The present method is excellent yields, eco-friendly, shorter reaction time, inexpensive and readily available catalyst.The simple and efficient procedure for a four-component condensation of benzil, aromatic aldehydes, ammonium acetate and 8-hydroxy-7-iodoquinoline-5-sulfonic acid (HISA) as the catalyst under microwave irradiation in mild reaction conditions to synthesis some of 2,4,5-triarylsubstituted imidazole derivatives. The present method is excellent yields, eco-friendly, shorter reaction time, inexpensive and readily available catalyst.

Starting from 4-aminohippuric acid (AHA), two novel series of heterocyclic compounds of pharmaceutical interest have been synthesised by one-pot, multicomponent reactions under microwave conditions. Reaction of AHA with various aldehydes and benzil in (1:1) EtOH/acetic acid in the presence of ammonium acetate yielded 1,2,3,5-tetra-arylated imidazole derivatives, whereas a solvent-free reaction of AHA with various aldehydes and dimedone (2 equiv.) in the presence of p-TSA yielded 4,9-diarylated 1,8-dioxo-decahydroacridine derivatives. These reactions produced good yields in short reaction times with an easy work-up, and purification of products was achieved by simple recrystallisation.

A one pot four-component reaction of 9,10-phenanthraquinone, aromatic aldehyde, aniline, and ammonium acetate was designed for the preparation of tetrasubstituted imidazoles (phenanthro[9,10-d]imidazole) derivatives in the presence of SBA-Pr-SO3H as a mesoporous solid acid catalyst. Phenanthro[9,10-d]imidazole derivatives were produced by the use of this technique in short reaction times and good to high yields. SBA-15 (Santa Barbara Amorphous), as a hexagonal mesoporous silica with 6 nm pore diameter, was synthesized and then its internal surface was modified with (3-mercaptopropyl)trimethoxysilane following an oxidation process to gain SBA-Pr-SO3H. The latter was then characterized; SEM image showed uniform particles about 700-900 nm and TEM image demonstrated the presence of parallel channels, which resemble the pores configuration of SBA-15. Additionally, the weight reduction in TGA curve in the temperature range of 200-600 °C (about 20% mass loss) established that the anchored propyl sulfonic acid groups onto the SBA-15 pores is about 1.2 mmol/g. This data was also confirmed by back-titration of SBA-Pr-SO3H with standardized NaOH and HCl solutions.

Synthesis and X-ray structure of novel 2- and 3-heteroatom-substituted ansa-zirconocene complexes

Green synthesis and characterization of trisubstituted imidazole derivatives by an ecofriendly and efficient heterogenous nanocatalyst based on magnetite nanoparticles coated modified nanocellulose

Development of chlorotriazine polymer dehydrocondensing reagents (Poly-Trzs)

Efficient process technologies for the preparation of 2'-substituted nucleoside monomers, as well as for oligonucleotide preparation, are introduced. A novel method for efficient preparation of 2'-substituted uridines is presented. This method employs the 3'-hydroxyl group of 2,2'-anhydrouridine as a tether for the facile intramolecular introduction of nucleophiles to the 2'-position. It allows access to 2'-alkoxy substituents from their alcohol precursors and to substituted 2'-amino substituents, such as the novel O-substituted 2'-hydroxylaminouridines. A novel process for large-scale oligonucleotide synthesis is discussed, which allows solution phase coupling of the monomer to the growing oligonucleotide chain. This is followed by selective isolation of productive coupling product by anchoring to a resin. Release from this resin completes a coupling cycle.

Insight on development of oxazole and imidazole derivatives as COX inhibitors with anti-inflammatory effects

Numerous aryl bromides and iodides react with acetone enolate ion in liquid ammonia under irradiation to form arylacetones in high yield. This synthesis is successful with bromo-or iodobenzene derivatives carrying alkoxy, alkyl, phenyl, halogen, and carboxylate substituents, and with halogen derivatives of polynuclear aromatic hydrocarbons. The method is remarkably insensitive to steric hindrance ; for example, 2, 4, 6-triethylbromobenzene reacts quite well. With greater steric hindrance, as in 2, 4, 6-triisopropyliodobenzene, reactivity falls and a side reaction of dehalogenation becomes appreciable, for reasons which are suggested. The synthesis was unsuccessful with the diethylamino, nitro and ionized hydroxy (-O-) substituents. Potassium metal-stimulated reactions of a few aryl diethyl phosphates with acetone enolate ion give generally lower yields of arylation and larger yields of dephosphation (hydrocarbon) products, compared even to potassium-stimulated reactions with aryl bromides. It is postulated that the lesser formation of hydrocarbon products from the aryl bromides is related to transport effects and solution inhomogeneity.

A novel and convenient route to the first poly(ferrocenylsilanes) with alkoxy, aryloxy, and amino substituents at silicon is reported. The reaction sequence involves (i) unexpectedly facile and clean halogen replacement at the bridging atom of a readily accessible dichlorosilyl‐bridged [1]ferrocenophane by OR, OAr, and NR2 groups via reactions with aliphatic and aromatic alcohols and amines in the presence of an HCl acceptor and (ii) thermal or transition metal catalyzed ring‐opening polymerization of the new ferrocenophane.

Cross-linked poly(4-vinylpyridine) supported Fe3O4 nanoparticles, abbreviated as [P4-VP]-Fe3O4NPs, were easily prepared as a new magnetic polymeric catalyst and efficiently used for the synthesis of imidazole derivatives. The polymeric catalyst was characterized by using of various techniques including field emission scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry and Fourier transform infrared spectroscopy (FT-IR) techniques. According to the obtained results, good dispersion of Fe3O4 nanoparticles on the polymer-support and excellent magnetic property of the catalyst were achieved. Various methods have been reported for the synthesis of multi-substituted imidazoles by the reaction of benzil, aldehydes and amines or ammonium acetate in the presence of various catalysts. These methods have some disadvantages including long reaction times, non-reusability of the catalyst, polluted reaction conditions, effluent pollution, and low yields; therefore, we wish to report an efficient, fast, clean and green method for the synthesis of imidazole derivatives that has been developed by one-pot condensation reaction of benzil, ammonium acetate and aldehydes in the presence of [P4-VP]-Fe3O4 nanoparticles. The catalyst displayed good catalytic activity when applied for the synthesis of imidazole derivatives. Various imidazole derivatives were prepared in high to excellent yields (68–99%) with short reaction time and high purity. The present procedure offers advantages such as short reaction time, simple reaction work-up, and the polymeric catalyst can be regenerated and reused several times without significant loss of its activity.

The multi-component condensation of benzil, primary amines, ammonium acetate and various aldehydes was efficiently catalyzed using cobalt oxide nanoparticles under ultrasonic irradiation. This approach describes an effective and facile method for the synthesis of some novel 1,2,4,5-tetrasubstituted imidazole derivatives with several advantages such as high yields and short reaction times and reusability of the catalyst. Moreover, the prepared heterocyclic compounds showed high antibacterial activity against some pathogenic strains. The facile and efficient approaches for the preparation of Co3O4 nanoparticles were carried out by one step method. The synthesized heterogeneous nanocatalyst was characterized by spectroscopic analysis including EDX, FE-SEM, VSM, XRD and FT-IR analysis. The as-synthesized cobalt oxide nanoparticles showed paramagnetic behaviour in magnetic field. In addition, the catalytic influence of the nanocatalyst was examined in the one-pot reaction of primary amines, benzil, ammonium acetate and diverse aromatic aldehydes under ultrasonic irradiation. All of the 1,2,4,5-tetrasubstituted imidazoles were investigated and checked with m.p., 1H NMR, 13C NMR and FT-IR spectroscopy techniques. The antibacterial properties of the heterocycles were evaluated in vitro by the disk diffusion against pathogenic strains such as Escherichia coli (EC), Bacillus subtillis (BS), Staphylococcus aureus (SA), Salmonellatyphi (ST) and Shigella dysentrae (SD) species. In this research cobalt oxide nanostructure was used as a robust and green catalyst in the some novel imidazoles. The average particle size measured from the FE-SEM image is found to be 20-30 nm which confirmed to the obtained results from XRD pattern. Various electron-donating and electron-withdrawing aryl aldehydes were efficiently reacted in the presence of Co3O4 nanoparticles. The role of the catalyst as a Lewis acid is promoting the reactions with the increase in the electrophilicity of the carbonyl and double band groups. To investigate the reusability of the catalyst, the model study was repeated using recovered cobalt oxide nanoparticles. The results showed that the nanocatalyst could be reused for five times with a minimal loss of its activity. We have developed an efficient and environmentally friendly method for the synthesis of some tetrasubstituted imidazoles via three-component reaction of benzil, primary amines, ammonium acetate and various aldehydes using Co3O4 NPs. The present approach suggests different benefits such as: excellent yields, short reaction times, simple workup procedure and recyclability of the magnetic nanocatalyst. The prepared 1,2,4,5-tetrasubstituted imidazoles revealed high antibacterial activities and can be useful in many biomedical applications.