Sosale Chandrasekhar

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, Bronsted acids, strong Lewis acids and by-products, and a simple work-up characterise the procedures.

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.

Improved procedures for the Beckmann rearrangement: the reaction of ketoxime carbonates with boron trifluoride etherate

A variety of ketoxime ethyl carbonates-easily prepared from the oximes and ethyl chloroformate-undergo the Beckmann rearrangement upon treatment with 1 equivalent of boron trifluoride etherate, in dichloromethane solution at room temperature in excellent yields (generally 75-99%)

A bifunctional approach towards the mild oxidation of organic halides: 2-dimethylamino-N,N-dimethylaniline N-oxide

Abstract The titled reagent incorporates an oxygen-centred nucleophile and a basic moiety—in a suitably mutual orientation—in the same molecule. It oxidises various primary benzylic bromides to the corresponding aromatic aldehydes under relatively mild conditions (MeCN/rt–50°C/6–24 h) in high yields (83–97%), and is thus a useful alternative to the Kornblum procedure.

Beckmann rearrangement in the solid state: reaction of oxime hydrochlorides

Several ketoxime hydrochlorides undergo Beckmann rearrangement upon heating below their melting points for 5-48 h, in excellent yields (generally >70%). The absence of a reaction solvent and of by-products (except for HCl) makes for a very simple work-up. Aldoxime hydrochlorides apparently undergo dehydration to the corresponding nitriles under the above conditions. Dibenzyl ketoxime hydrochloride unexpectedly furnished a pyrazine derivative (67%), presumably via further reaction of the intermediate nitrilium ion in the crystal lattice.

Evidence for a Stereoelectronic Effect in the Baeyer-Villiger Reaction: Introducing the Intramolecular Reaction

An intramolecular Baeyer-Villiger reaction has been effected involving a conformationally-fixed intermediate which breaks down with stereoelectronic control.

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

Crystal structure of an intermolecular 2:1 complex between adenine and thymine. Evidence for both Hoogsteen and 'quasi-Watson-Crick' interactions.

CH_2Cl_2

The principle of microscopic reversibility in organic chemistry - a critique

at room temperature

Chiral Mitsunobu reactions with (1S)-(+)-ketopinic acid: kinetic resolutions of secondary alcohols

The titled complex, obtained by co-crystallization (EtOH/25 degrees C), is apparently the only known complex of the free bases. Its crystal structure, as determined by X-ray diffraction at both 90 K and 313 K, showed that one A-T pair involves a Hoogsteen interaction, and the other a Watson-Crick interaction but only with respect to the adenine unit. The absence of a clear-cut Watson-Crick base pair raises intriguing questions about the basis of the DNA double helix.