Oxalic acid:A very useful bronsted acid in organic synthesis

(A) Oxalic acid is an efficient reagent for the Beckmann reaction - a variety of ketoximes are converted into the corresponding secondary amides by classical anti-periplanar migration upon heating to ca. 100 °C, and aldoximes afford the corresponding nitriles. The procedure offers high yield of the desired products, gaseous byproducts $(CO + CO_2)$ and the absence of reaction solvent. (B) Anhyd. oxalic acid is an excellent mediator for one-pot transformation of ketones to amides in the presence of hydroxylamine hydrochloride. The method is effective for various arom. and aliph. ketones, and provides excellent yield of the products. (C) In the presence of aq. oxalic acid, enol ethers undergo expeditious hydrolysis to the corresponding ketones without concomitant migration of the double bond. In contrast, use of a mineral acid typically gives the conjugated ketone. This method offers considerable advantage in terms of regioselectivity of the product

Beckmann reaction of oximes catalysed by chloral: mild and neutral procedures

A variety of ketoximes undergo the Beckmann rearrangement when heated with 0.5 molar equiv. of chloral (neat melt/1\sim30°C), to furnish the corresponding amides in excellent yields (generally 80–95%) after simple work-up. (Aromatic aldoximes dehydrated to the corresponding nitriles in excellent yields under similar conditions.) The absence of solvent, Brønsted acids, strong Lewis acids and by-products, and a simple work-up characterise the procedures

Effective ‘non-aqueous hydrolysis’ of oximes with iodic acid in dichloromethane under mild, heterogeneous conditions

Ketoximes and aromatic aldoximes are converted to the corresponding carbonyl compounds in excellent yields (67–97%), upon treatment with a suspension of iodic acid in dry $CH_2Cl_2$ at room temperatur

Ketones to amides via a formal Beckmann rearrangement in 'one pot': a solvent-free reaction promoted by anhydrous oxalic acid. Possible analogy with the Schmidt reaction

A variety of ketones can be directly converted into the secondary amides expected from a Beckmann rearrangement of the corresponding oximes in high yield, by heating them with hydroxylamine hydrochloride and anhydrous oxalic acid at similar to 100degreesC for 4-12 h. (Aromatic aldehydes afforded mixtures of nitrile and amide.) The transformation is apparently (kinetically) driven by the coupled decomposition of oxalic acid (to CO+CO2) via the fragmentation of an intermediate oxime mono-oxalate. However, an alternative pathway, mechanistically analogous to the Schmidt reaction, is not only equally likely but may well be general for the Beckmann rearrangement

Beckmann rearrangement of ketoximes on solid metaboric acid: a simple and effective procedure

When ketoximes admixed with solid metaboric acid (formed from boric acid at 100degreesC/0.1 Torr) are heated (similar to 140degreesC/7-42 h), the corresponding amides or lactams are produced in excellent yields (62-92%) via the Beckmann reaction. Aromatic aldoximes undergo both dehydration to the nitrile as well as (non-stereospecific) rearrangement under the above conditions. The absence of solvent, and the mildness and low toxicity of boric acid, characterise the present procedure. CO. 2002 Elsevier Science Ltd. All rights reserved

<i>Justicia</i> lignans: Part 9^† - Two new lignans from <i>Justicia neesii</i> Ramamoorthy (white flower variety)

596-600The isolation and characterization of a new arylnaphthalide lignan, named justicidin G1 and a new benzofuranoid neolignan, named tiruneesiin 2, in addition to four known arylnaphthalides, namely, jusmicranthin ethyl ether, lignan Jl 3, taiwanin E methyl ether 4, Jusmicranthin and two diphyllin glycosides, neesiinoside A and neesiinoside B have been reported from J. neesii (white flower variety). Structure elucidation of 1 and 2 is based on 2D NMR data and chemical transformations. Isolation of 2 is the first report of a neolignan from Justicia genus

Anion (Fluoride)-Doped Ceria Nanocrystals: Synthesis, Characterization, and Its Catalytic Application to Oxidative Coupling of Benzylamines

Fluoride doping in the CeO₂ lattice has been achieved by a simple, reliable, reproducible, and safe solution-based method. F-containing CeO₂ has retained the fluorite structure, and its effect has been confirmed from various analytical techniques such as powder X-ray diffraction, Fourier transform IR, Raman, UV–visible diffuse reflectance, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS), scanning electron microscopy–energy-dispersive X-ray (EDX) and transmission electron microscopy–EDX analysis. The concentration of fluoride in the CeO₂ lattice has been determined from chemical analysis and core-level XPS analysis. The concentration of Ce³⁺ in the F-doped and undoped CeO₂ samples have been determined both from XPS analysis as well as from variable-temperature magnetic susceptibility measurements. The characteristic Ce³⁺ emission in the PL spectrum indicated the increase of Ce³⁺ ion concentration in the F-doped sample, conforming to the results from XPS and magnetic measurements. F-doped CeO₂ nanocrystals showed moderate monodispersity as determined from particle-size measurements using dynamic light scattering experiments and high surface area of 106.1 m²/g. Optical band gap of CeO₂ has narrowed upon doping with fluoride ions from 3.05 to 2.95 eV. The formation of extrinsic oxygen vacancy complexes upon F-doping has been observed in the Raman spectrum (at 1097 cm^–1) in addition to fingerprint bands of CeO₂. The UV-shielding property and photocatalytic inactivity toward aqueous dye degradation process of F-doped CeO₂ has suggested its potential use in cosmetic applications. Both F-doped CeO₂ and CeO₂ have been used as catalysts for oxidative coupling of benzylamines to imines in the presence of molecular oxygen under solvent-free conditions. F-doped CeO₂ exhibited better catalytic efficiency than CeO₂. The oxidation procedure using these catalysts is simple, environmentally benign, and solvent-free, and the catalysts are reusable