Reactions of polyfluoro-arenols and -heteroarenols with activated dimethyl sulphoxide. Facile [2,3]-sigmatropic rearrangement reactions giving de-aromatised products

Contrasting behaviour is observed when 2- and 4-methoxy-3,5-dinitropyridine interact with methoxide ion in dimethyl sulphoxide. The 4-methoxy compound affords both methine and acetal sigma complexes, the latter being thermodynamically more stable. The interconversion is catalysed by methanol. Labelling experiments have established that the sigma complex from the 2-methoxypyridine is formed by addition at C6; no conversion into the acetal could be effected. These observations are rationalized in terms of differential steric and solvation effects. Demethylation and rearrangement reactions of 4-methoxy-3,5-dinitropyridine are reported.

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Catalyst-Free [2,3]-Sigmatropic Rearrangement Reactions of Photochemically Generated Ammonium Ylides

Synthesis ◽

10.1055/s-0037-1610732 ◽

2019 ◽

Vol 51 (23) ◽

pp. 4348-4358 ◽

Cited By ~ 1

Author(s):

Fang Li ◽

Feifei He ◽

Rene M. Koenigs

Keyword(s):

Visible Light ◽

Sigmatropic Rearrangement ◽

Tertiary Amines ◽

Amino Esters ◽

Catalyst Free ◽

Rearrangement Reaction ◽

Rearrangement Reactions ◽

Free Ammonium

The rearrangement reaction of ammonium ylides furnishes valuable α,α-disubstituted amino esters. In this work, we describe the visible-light photolysis reaction of aryldiazoacetates in the presence of tertiary amines that react via a free ammonium ylide in a sigmatropic rearrangement reaction to provide amino esters in moderate to very good yields (33 examples, up to 97% yield).

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Kinetics and Mechanism of Oxidation of Aliphatic Secondary Alcohols by Benzimidazolium Fluorochromate in Dimethyl Sulphoxide Solvent

Oriental Journal Of Chemistry ◽

10.13005/ojc/370315 ◽

2021 ◽

Vol 37 (3) ◽

pp. 626-633

Author(s):

Bhawana Arora ◽

Jitendra Ojha ◽

Pallavi Mishra

Keyword(s):

Activation Parameters ◽

Sigmatropic Rearrangement ◽

Dimethyl Sulphoxide ◽

Secondary Alcohols ◽

Hydrogen Ions ◽

Reaction Conditions ◽

First Order Kinetics ◽

Aqueous Solvent ◽

Ester Formation ◽

Different Temperatures

Oxidation of secondary alcohols is an important part of synthetic organic chemistry. Various studies are carried out at different reaction conditions to determine the best mechanistic pathways. In our study, oxidation of different secondary alcohols was done by using Benzimidazolium Fluorochromate in Dimethyl Sulphoxide, which is a non-aqueous solvent. Oxidation resulted in the formation of ketonic compounds. The reaction showed first order kinetics both in BIFC and in the alcohols. Hydrogen ions were used to catalyze the reaction. We selected four different temperatures to carry out our study. The correlation within the activation parameters like enthalpies and entropies was in accordance with the Exnerʼs criterion. The deuterated benzhydrol (PhCDOHPh) oxidation exhibited an important primary kinetic isotopic effect (kH / kD = 5.76) at 298 K. The solvent effect was studied using the multiparametric equations of Taft and Swain. There was no effect of addition of acrylonitrile on the oxidation rate. The mechanism involved sigmatropic rearrangement with the transfer of hydrogen ion taking place from alcohol to the oxidant via a cyclic chromate ester formation.

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