Journal of Chemical Research

A mechanism involving the formation of complex between benzilic acid and permanganate has been proposed for the title reaction and activation parameters for the slow step of reaction and reaction constants involved in the mechanism were calculated and discussed.

We report on glutamic acid rotation and its stable conformer in gas phase. The calculations were performed by HF/6-31G* and B3lyp/6-31G* levels of theory. There is a pertubation in the population diagram of the C3 that shows nucleophilic or radical attack will probably occur at this site. This fact is confirmed by the charge distribution and CSA (chemical shift anisotropy) diagrams. The energies and the relative energies are given as a function of rotational angle. Also, low and high-energy barriers of N-H rotation computed at various level of theory have been obtained. Vibrational frequencies of the structure were done to verify the minima of the energy.

Substituted 6-(1H-benzimidazol-2-yl)-[1,2,4]triazolo[3,4-a]phthalazine derivatives containing alkyl, aryl, hydroxyl, mercapto, methylthio and formyl substituents at position 3 have been synthesised. Di-[6-(1H-benzimidazol-2-yl)-3-[1,2,4]triazolo[3,4-a]phthalazin-3-yl]alkanes have been obtained by the use of dicarboxylic acids or their esters in the above condensations. Methylation reactions of the triazolo-phthalazine system are reported.

Zn/NH₄Cl–mediated reactions of aldehyde 1 with nitro compounds 2 afford 2-(N-alkyl/arylamino)-3-formylchromones 4, which on heating with 70% H₂SO₄ produces 9a-d and 11e-h from 4a-d and 4e-h, respectively.

Efficient syntheses of naturally occurring linear dihydronaphthopyran (6a) and its angular analogues (3b and 4), from appropriate ortho-methoxynaphthaldehydes, have been described.

Upon UV irradiation 2-alkoxy substituted benzophenones 2a–f and ethyl-2-aroyl aryloxy acetates 7a–c, in acetonitrile under went intramolecular δ hydrogen abstraction and led to synthesis of solely dihydrobenzofuranols 6a–f and 11a–c in excellent yield with potent antimicrobial activity.

Based on the different reactivities of iodo-groups and tributylstannyl groups, (E)-α-iodovinylstannanes can undergo sequential cross-coupling reactions in the presence of a palladium(0) catalyst to form two carbon-carbon bonds to the same olefinic carbon leading to trisubstituted alkenes stereoselectively.

The first structurally characterised uranyl bis (β-diketonate)-amide adduct compound [UO₂(DBM)₂. C₄H₉CON (3-C₅H₁₁) (sec-C₄H₉)] (DBM = dibenzoylmethanate) shows that the amide ligand bonded through its amido oxygen atom to the uranyl group. The average bond distances for U–O_(uranyl), U–O_(DBM) and U–O_(amide) are 1.778(5), 2.346(5) and 2.411(5)Å respectively.

A concise route to the title compound was achieved via annulation of 4,4-dimethylcyclohexenone with 3-cyanophthalide, followed by oxidation with DDQ.

Allylsamarium bromide reacts with α, β-unsaturated alkynones to afford reginospecific nucleophilic addition products in good yields under mild conditions.

The stereochemistry of 3β,17β-dihydroxy-3α-ethylandrost-4-ene, 3α,17β-dihydroxy-3β-methylestr-4-ene and 3β-acetoxy-7α,17β-dihydroxy-7β-methylandrost-5-ene, which were obtained by Grignard reactions from the corresponding αβ-unsaturated ketones, have been established by X-ray crystallography.

Autoxidation of isotachysterol under atmospheric oxygen in the dark at ambient temperature produces two new epoxides: (3S,5R)- and (3S,5S)-5,10-epoxy-isotachy sterols.

Racemic 2-isoxazoline-5-carboxylate esters were reduced under mild conditions to form the corresponding primary alcohols. These alcohols were enzymically resolved by acylation with succinic anhydride in the presence of Amano AK lipase.

A new host compound, 2,7-bis-(3-hydroxy-3,3-diphenyl-prop-1-ynyl)-fluoren-9-one (2), shows guest-selective colour change and fluorescence enhancement upon inclusion complexation in the solid state.

Hydromagnesiation of alkynylsilanes gives (Z)-α-silylvinyl Grignard reagents, which are cross-coupled with alkynyl iodides in the presence of tetrakis(triphenylphosphine)palladium(0) catalyst to afford stereoselectively 1,3-enynylsilanes in good yields.

Ammonium acetate condenses with benzoxazinones (4b–e) or a mixture of anthranilic acid and orthoesters in the absence of solvent to produce the title compounds in a few minutes.

A copper(II) complexes of calix[4]arene tetraimidazole (CTI) ligand has been prepared to mimic the active site of copper metalloproteins.

Aromatic and aliphatic aldoximes were catalytically oxidised to carboxylic acid esters in good to moderate yields with hydrogen peroxide as oxidant using polystyrene-bound phenylseleninic acid as catalyst.

The sulfonation of aromatic amines with high yields, simple operations and short reaction time has been studied under microwave irradiation in solvent-free conditions.

Three complexes, [M(CO)₅Tz], have been synthesised by the photochemical reaction of 3,5-dimethyl-1,2,4-triazole (Tz) with [M(CO)₆] (M = Cr, Mo and W). The crystal structure of [Cr(CO)₅Tz] has been characterised by X-ray analysis, and the 4H-tautomer of the triazole ligand is observed in this complex in the solid state.

A mild and efficient method for the mononitration of aromatic and olefinic compounds is described. This method is especially useful for active substrates.

The useful synthetic reagent trimethylsilyl cyanide was readily prepared in high yield by the cyanation of trimethylchlorosilane with potassium cyanide in the presence of PEG400 and zinc iodide under stirring at room temperature or ultrasonic radiation.

β-Alanine is an amino acid which is important in the design of diverse peptides. Crystallographic study shows that the N-acyl adduct of β-Alanine, an ω-amino acid important in peptide design for the production of structural and functional diversities, and N,N′-dicyclohexyl urea(DCU) forms a turn like structure without any intra-molecular hydrogen bonding.

An efficient method for the synthesis of (+)-coronarin E 1, (+)-epi-coronarin A 2 and (+)-15, 16-epoxy-8(17), 13(16), 14-labdatriene 3 via the homodrimane 9, obtained in four steps from (+)-manool 5, is described.

1,2-Dicarbonyl compounds employed as key-intermediates in indolone-N-oxide synthesis were prepared by direct oxidation of aryl, aryl- and aryl, alkyl-substituted alkenes assisted by benzeneseleninic anhydride.

A new (1) and a known (2) β-dihydroagarofuran sesquiterpene polyol ester were isolated from Euonymus nanoides and they showed antitumor activities in vitro.

Deep, persistent, but structurally sensitive photoyellowing observed in photochemical studies of a wide range of arylsulfonyl derivatives of amines, amino acids and peptides can be attributed to a novel kind of photochromism in which intramolecular photoinduced electron transfer promotes the formation of a metastable cyanine-type chromophore involving sulfur d-orbitals.

Pyrimidin-2-one and pyrimidine-2-thione derivatives 5 and 7 are obtained in 40-65% and 60-75% yields when 4-ethoxycarbonyl-5-phenylfuran-2,3-dione (1) react with semicarbazones, thiosemicarbazones 2a–f, urea and thiourea derivatives 6a–d through loss of water and carbon dioxide.

A practical and chemoselective method for the reduction of N-protected amino acids and peptides including carboxylic acids to their corresponding alcohols is outlined.

Room temperature powder infrared and Raman measurements for the new melaminium salt, bis(2,4,6-triamino-1,3,5-triazin-1-ium) sulfate dihydrate, 2C₃H₇N₆⁺·SO₄^2-·2H₂O, in the crystalline state, were carried out. The vibrational spectra in the region of internal vibrations of the ions corroborate recent X-ray data of Janczak et al. Some spectral features of this new crystal are referred to those of other crystalline melaminium salts.

Structurally different aliphatic and aromatic carboxylic acids and anhydrides are efficiently reduced to their corresponding alcohols with a new modified zinc tetrahydroborate agent, (pyridine)(tetrahydroborato)zinc complex, [(Py)Zn(BH₄)₂], in refluxing THF.