Organic Chemistry Research
Volume:2 Issue: 1, Winter 2016

A highly efficient procedure for the synthesis of 1,8-dioxo-octahydroxanthenes under mild, green and solvent-free condition by using HOSA as a dual role catalyst is described. This is the first report of catalytic activity of HOSA.

A sequential process strategy was introduced for the synthesis of 2,3,4,5-tetrasubstituted pyrroles by the formation of benzoin from the corresponding aromatic aldehyde and followed by condensation reaction with 1,3-dicarbonyl compounds and ammonium acetate in the presence of diethylene glycol-bis(3-methylimidazolium) dihydroxide as catalyst in refluxing ethanol. The recycled catalyst could be reused four times without appreciable loss in the catalytic activity.

Cobalt hydrogensulfate is an efficient catalyst for the condensation of β-naphthol, aromatic aldehydes and 5,5-dimethyl-1,3-cyclohexanedione at 120 °C to afford 9,9-dimethyl-12-phenyl-8,10,11,12-tetrahydro-9-H-benzo[a]xanthen-11-one derivatives in high yields. Also, polycondensation reactions of phenols with phthalic anhydride were carried out in the presence of cobalt hydrogensulphate under solvent-free conditions. Simple and convenient procedure, high conversion, reusability of catalyst, easy purification and short reaction time are the advantageous features of this method.

In this paper, 4,4ʹ-bipyridinium dichloride  supported SBA-15 (SBA@BiPy2+ 2Cl-) was used for the synthesis of dihydropyrimidinones. The synthesized catalyst was characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Thermogravimetric analysis (TGA). This nanocomposite was shown to be an efficient heterogeneous catalyst for the synthesis of dihydropyrimidinones derivatives via one-pot multicomponent method under solvent-free conditions. In addition, the catalyst can be recycled several times with no significant loss of catalytic activity.

In this researchsaccharomyces cerevisiae (baker’s yeast) was used as a cheap, readily accessible, selective, efficient, and green bio-catalyst in a chemo selective reduction of carbonyl group to hydroxyl group. In this green procedure three substrates e.g. (3-(3-nitrophenyl)aziridin-2-yl)-1-phenyl-methanone, pyruvate ester, and 2-acetyl-γ-butyrolactone were reduced to their corresponding reduced compounds in the presence of saccharomyces cerevisiae atambient temperature in aqueous media. It was worthy to note that ketone groups were chemo-selectively reduced, while ester and lactone groups remained unchanged. Moreover, in this procedure, chemo selective bio-reduction of ketone group to hydroxyl group can be performed by coenzyme NADPH in saccharomyces cerevisiae (baker’s yeast) which is recyclable in water, as a green solvent, while this recyclization cannot occur in non-aqueous systems. The structure of products was confirmed by IR and 1H NMR spectra.

Molecular structure, isomerism, conformational stability and intramolecular hydrogen bonding (IHB) of cis-enol forms of 1-(n-pyridyl)butane-1,3-diones (nPBD) (n = 2, 3, or 4) have been investigated by means of density functional theory (DFT) calculations. Energy differences for all possible nPBD cis-enol forms of isomers with respect to the most stable form of the corresponding isomer have been estimated in the gas phase and solution. AIM results (performed at the B3LYP/6-311++G** level) suggest 75.19-84.77 kJ mol-1 for the strength of intramolecular hydrogen bond in these systems, as a medium hydrogen bond strength. Theoretical structure, NBO and intramolecular hydrogen bond strength for the stable cis-enol forms of nPBD have been compared with each other and also with those of acetylacetone (AA), benzoylacetone (BA), and triflouroacetylacetone (TFAA) molecules. The hydrogen bond strength and molecular stability are investigated by applying the NBO, topological analysis, geometry calculations, and spectroscopic results. The correlation between IHB and some parameters related to hydrogen bonding have been also investigated.

One-pot preparation of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles has been conducted in the presence of poly(4-vinylpyridinium butane sulfonic acid) hydrogen sulfate, P(4VPBSA)HSO4, as an efficient dual acidic catalyst under solvent-free conditions. Reusability of the catalyst, easy work-up procedure, eco-friendly reaction conditions, short reaction times and high yields of the products illustrate the utility of this approach.

In this study an easy, green, efficient and simple approach is reported for the synthesis of some benzothiazole-, benzimidazole- and benzoxazole-2-thiolderivatives. The proposed approach employs the reaction of corresponding aromatic amine with potassium isopropyl xanthate (Z11) in the presence of copper sulfate (CuSO4) as a catalyst under conventional heating and ultrasonic irradiation. The advantages of this protocol are: using water and glycerol as green solvents, commercially available precursors, simple work-up, an inexpensive catalyst, high yield and short reaction time.

One main group of organic chemistry is related to the aromatic compounds. In the present work, we replaced the CH group of benzene by silicon and nitrogen analogues. Then, Density functional theory (DFT) calculations were carried out for six-membered heterocyclic Si-N aromatic rings. Full geometry optimizations were performed in gas-phase, and at B3LYP level using 6-311++G(d,p) and CBSB7 basis sets. Here, the stability and aromatic properties of the molecules were investigated. It was observed that the molecule 1,3,5-triaza-2,4,6-trisiline shows high kinetic stability and low chemical reactivity. Total energies, nucleus-independent chemical shift (NICS) and HOMO-LUMO gap values were calculated to determine the stability, aromaticity and reactivity of azasilines. NICS calculations denoted high aromatic property for hexasiline and hexazine. We also considered seven different isodesmic reactions for stabilization energy (SE) calculations of molecules. The molecule 1,4,5,6-tetraaza-2,3-disiline showed the greatest aromatic stabilization among all molecules.

Cellulose was applied as a reusable and green catalyst for the facile four-component synthesis of 6-amino-4-aryl-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile derivatives using hydrazine monohydrate, ethyl acetoacetate, malononitrile and aryl aldehydes, under solvent-free and thermal conditions. The use of non-toxic and inexpensive catalyst, short reaction time, clean work-up and good yields of the products are advantages of this method.

In this research, SO3H-functionalizedphthalimide (SFP) has been prepared through simple reaction of phthalimide with chlorosulfonic acid, and characterized using FT-IR, 1H NMR, 13C NMR, SEM (scanning electron microscopy), mass and TG (thermal gravimetric) spectra. Afterward, the solid acid has been utilized as an efficient, green, heterogeneous and recyclable catalyst for the solvent-free synthesis of 2-amino-4H-chromenes by the one-pot multi-component reaction of aromatic aldehydes with malononitrile and 1-naphthol under thermal (70 °C) and microwave (540 W) conditions.

The acetylation of various alcohols and phenols was performed successfully using acetic anhydride in the presence of Citric acid coated magnetite nanoparticles as catalyst under solvent-free condition and at 45 °C. The catalyst showed high thermal stability and was recovered and reused at least 5 times without any considerable loss of activity. The present process is environmentally benign and economical.