Search

It was discovered that the Kharasch peroxidation of barbituric acids proceeds both with a Cu-catalyst and without a metal catalyst. Despite the presence of possible thermal-initiated side oxidation pathways, α-tert-butylperoxybarbiturates were selectively prepared from substituted barbituric acids and tert-butyl hydroperoxide.

The instability of hydroxy peroxyesters, the elusive Criegee intermediates of the Baeyer-Villiger rearrangement, can be alleviated by selective deactivation of the stereoelectronic effects that promote the 1,2-alkyl shift. Stable cyclic Criegee intermediates constrained within a five-membered ring can be prepared by mild reduction of the respective hydroperoxy peroxyesters (β-hydroperoxy-β-peroxylactones) which were formed in high yields in reaction of β-ketoesters with BF3 ⋅Et2 O/H2 O2 .

In this work we found that a H2O2–HBr(aq) system allows synthesis of α-monobromo ketones and α,α′-dibromo ketones from aliphatic and secondary benzylic alcohols with yields up to 91%. It is possible to selectively direct the process toward the formation of mono- or dibromo ketones by varying the amount of hydrogen peroxide and hydrobromic acid. The convenience of application, simple equipment, multifaceted reactivity, and compliance with green chemistry principles make the application of the H2O2–HBr(aq) system very attractive in laboratories and industry. The proposed oxidation–bromination process is selective in spite of known properties of ketones to be oxidized by the Baeyer–Villiger reaction or peroxidated with the formation of compounds with the O–O moiety in the presence of hydrogen peroxide and Bronsted acids.

Malonyl peroxides were used for the one-pot construction of hybrid structures by conjugation of heterocycle (3H-pyrazol-3-one, isoxazol-5(2H)-one, pyrazolidine-3,5-dione, or barbituric acid) and amine or alcohol. The first stage represents oxidative C–O coupling with liberation of the carboxyl group which is functionalized at the second stage thus affording ‘clicklike’ products with malonic linker.

For the first time silica gel was observed to activate peroxides in oxidative coupling reactions. Here we report silica gel mediated oxidative C–O coupling of β-dicarbonyl compounds with cyclic diacyl peroxides affording α-acyloxy derivatives with 100% atom efficiency. The highest yields of coupling products were achieved in solvent free conditions. C–O coupling products were prepared in yields up to 86%.

The electrochemically induced cross-dehydrogenative C–O coupling of β-diketones and β-ketoesters (C–H reagents) with carboxylic acids (O–H reagents) was developed. An important feature of this reaction lies in the selective formation of intermolecular C–O coupling products in high yields, up to 92%, using DMSO as a solvent with a broad substrate scope in an undivided cell equipped with carbon and platinum electrodes at high current density. Electric current acts as a stoichiometric oxidant.

A two-step, one-pot reaction of aldehydes with the CAN/LiBr oxidation system under solvent-free conditions followed by the addition of methanol affords methyl α-bromocarboxylates. The oxidation of aldehydes with methanol using this system gives only methyl esters. A facile method, which does not require special equipment, was developed for the synthesis of 2-bromoesters from aliphatic aldehydes with carbon chain lengths of 5–10 atoms.

The one-pot oxidation-chlorination of secondary alcohols to give α,α′-dichloro ketones in 62–80% yields is reported. The convenient and readily available H2O2/HCl system acts on secondary alcohols (C5-C17) with the formation of α,α′-dichloro ketones. The reaction proceeds with high selectivity under the reported conditions; during this process peroxide formation and the Baeyer-Villiger oxidation reactions are not observed.

Silica gel was found to mediate decarboxylation of tetracarbonyl compounds with a free carboxylic group prepared from β-dicarbonyl compounds and malonyl peroxides. Under solvent-free heterogeneous conditions silica gel effectively acts as a mediator of C–O coupling with further decarboxylation at 120 °C.

Reactions of β-diketones and β-keto esters with tert-butyl hydroperoxide under heterogeneous conditions using SiO2-supported copper(II) perchlorate as a catalyst give rise to α-peroxidation products in 65—82% yields. A possibility to reuse the catalyst was demonstrated.

A facile method, which does not require special equipment, was developed for the preparation of microsized cerium chloride by the thermal treatment of CeCl3·7H2O or the evaporation of its alcoholic solutions. The way of the preparation of the cerium chloride-based catalyst plays a decisive role in its catalytic activity. This catalyst is efficient in the Michael addition of β-diketones to vinyl ketones giving β,δ-triketones.

A facile method, which does not require special equipment, was developed for the preparation of microsized cerium chloride by the thermal treatment of CeCl3·7H2O or the evaporation of its alcoholic solutions. The way of the preparation of the cerium chloride-based catalyst plays a decisive role in its catalytic activity. This catalyst is efficient in the Michael addition of β-diketones to vinyl ketones giving β,δ-triketones.