Structure of the Boronic Acid Dimer and the Relative Stabilities of Its Conformers

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Kinetics of diamminesilver(I)-catalysed oxidation of sulphur(IV) by dioxygen in ammonia buffers

The kinetics of the silver(I)-catalysed autoxidation of SO₃ ^2– into SO₄ ^2– in ammonia–ammonium nitrate buffer obeyed the rate law:R _obs=k₁ k₂ K[Ag^I]_T[SO₃ ^2-}][O₂] / ([NH₃]+K[SO₃ ^2-])(k₁+k₂[O₂])The values of k ₁, k ₂/k _–1 and K were found to be 1.2l mol^–1 s^–1, 5.3 × 10² l mol^–1 and 0.6 respectively at 30 °C. Two alternative free radical mechanisms have been proposed.     

(1S,2R/1R,2S)-ainocyclohexyl glycyl thymine PNA: synthesis,monomer crystal structures,and DNA/RNA hybridization studies

[structure: see text] The synthesis of ethyl cis-(1S,2R/1R,2S)-2-aminocyclohex-1-yl-N-(thymin-1-yl-acetyl) glycinate (10a and 10b) via enzymatic resolution of the key racemic intermediate trans-2-azido cyclohexanols 3 is reported. The crystal structures of 10 show equatorial disposition of the tertiary amide group, with the torsion angle beta in the range 60-70 degrees. The PNA oligomers incorporating these show differential effects in hybridizing with complementary DNA and RNA.     

Determination of bromide and nitrite by indirect redox titration using phenyl iodosoacetate

Bromide has been determined by its oxidation with an excess of phenyl iodosoacetate in the presence of acetanilide to give bromine which subsequently reacts with acetanilide to form 4-bromoacetanilide. The residual amount of phenyl iodosoacetate was evaluated iodometrically. Thus, for every mol of bromide one mol of phenyl iodosoacetate was consumed. For the determination of bromine in organic compounds, the test substance was decomposed by fusion with alkali peroxide to liberate bromide which was then evaluated by the phenyl iodosoacetate method. For its determination, nitrite has been reacted with an excess of isoniazid in acid medium to form isonicotinyl azide (which does not react with phenyl iodosoacetate) and the residual amount of isoniazid was titrated with phenyl iodosoacetate in the presence of acidified bromide and methyl red indicator (when isoniazid and phenyl iodosoacetate react in a 12 molar ratio). Each mol of nitrite is equivalent to 2 mol of phenyl iodosoacetate.     

One-pot multistep Bohlmann-Rahtz heteroannulation reactions: synthesis of dimethyl sulfomycinamate

[reaction: see text] The synthesis of dimethyl sulfomycinamate, the acidic methanolysis product of the sulfomycin family of thiopeptide antibiotics, from methyl 2-oxo-4-(trimethylsilyl)but-3-ynoate is achieved in a 2,3,6-trisubstituted pyridine synthesis that proceeds with total regiocontrol in 13 steps by the Bohlmann-Rahtz heteroannulation of a 1-(oxazol-4-yl)enamine or in 12 steps and 9% yield by three-component cyclocondensation with N-[3-oxo-3-(oxazol-4-yl)propanoyl]serine and ammonia in ethanol.     

Synthesis,cytotoxic and antioxidant activities of azolyl benzothiazine carboxamides

Research on Chemical Intermediates - Azolyl benzothiazine carboxamides were prepared from benzothiazine carboxylate and azolyl amines in the presence of NaOMe under ultrasonication....     

Copper‐Catalyzed Oxidative C−H Bond Functionalization of N‐Allylbenzamide for Regioselective C−N and C−O Bond Formation

Copper‐catalyzed oxidative couplings of N‐allylbenzamides for C?N and C?O bond formations have been developed through C?H bond functionalization. To demonstrate the utility of this approach, it was applied to the synthesis of β‐aminoimides and imides. To the best of our knowledge, these are the first examples in which different classes of N‐containing compounds have been directly prepared from the readily available N‐allylbenzamides using an inexpensive catalyst/oxidant/base (CuSO₄/TBHP/Cs₂CO₃) system.     

Removal of cesium and strontium from acid solution using a composite of zirconium molybdate and zirconium tungstate

A composite mixture of zirconium molybdate and zirconium tungstate was prepared and studied for the sorption of cesium and strontium as a function of nitric acid, metal ion concentration, time and temperature. The distribution coefficient (K_d) of 7000 ml/g (~90% sorption) and 70 ml/g (~20% sorption) was obtained for the sorption of cesium and strontium in 0.1M nitric acid, respectively. Experimental sorption capacity, b for cesium was found to be 50 mg/g from 0.1M HNO₃ and 30 mg/g for strontium from 0.001M nitric acid. The sorption of strontium on the sorbent was accompanied by the absorption of heat but the sorption of Cs⁺ results in the liberation of heat. Column studies were conducted by following a breakthrough (BT) curve of cesium and strontium up to C/C₀=1 and the results are reported.     

Electrochemically induced one pot synthesis of 1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile derivatives via a four component-tandem strategy

An efficient one pot, multicomponent-tandem synthesis of highly functionalized 1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile is reported by electrochemically induced condensation of ethyl acetoacetate, hydrazine hydrate, malononitrile and various aromatic aldehydes. The reaction is carried out in an undivided cell, at a constant current in the presence of NaBr as a supporting electrolyte and ethanol as solvent.     

Harnessing the catalytic behaviour of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP): An expeditious synthesis of thioesters

A novel, efficient, metal-, base- and acid-free straightforward protocol has been developed for the construction of useful thioesters. The immense catalytic potential of HFIP for promoting the thiocarbonylation of acyl halides and thiols is disclosed. HFIP was recovered with ease and reused for further reactions without any loss of reactivity. Both aryl and alkyl thiols bearing electron-donating and electron-withdrawing groups as well as aryl- and alkyl acyl halides worked well in this reaction. Inexpensive precursors, short reaction time, obviating workup, high atom economy, and gram-scale preparation are the significant features of the developed eco-friendly route for S-carbonylation of thiols.