Multivariate optimization of the KharascheSosnovsky allylic oxidation of olefins

The multivariate optimization method known as simplex is applied to the KharascheSosnovsky allylic oxidation of double bonds. By applying this method, the amounts of three variables (copper source, oxidant, and additive) are optimized at the same time. Under the conditions thus obtained the reaction takes place in a considerable shorter time, being the alkene the limiting reagent. These conditions are applied to some monoterpenes and sesquiterpenes leading regioselectively to the corresponding benzoate esters, opening a route to the employment of this reaction in the synthesis of more complex molecules

Optimization by Response Surface Methodology (RSM) of the Kharasch−Sosnovsky Oxidation of Valencene

Response surface methodology (RSM) has been employed to model and optimize the Kharasch−Sosnovsky allylic oxidation of valencene. The detailed effects of the amounts of oxidant, substrate, copper catalyst, 1,8- diazabicyclo[5.4.0]undec-7-ene (DBU), and temperature have been studied. The concentration of substrate and quantity of oxidant have been determined as the most significant variables. The interaction effects on the yield have been investigated using a three-level full-factorial design. The yield of benzoyloxyvalencene has been improved to 99%. Analysis of variance (ANOVA) has been used to evaluate the goodness of fit of the model

Acyloxylation of 1,4-Dioxanes and 1,4-Dithianes Catalyzed by a Copper−Iron Mixed Oxide

The use of a copper−iron mixed oxide as a heterogeneous catalyst for the efficient synthesis of α-acyloxy-1,4-dioxanes and 1,4-dithianes employing t-butyl peroxyesters is reported. The preparation and characterization of the catalyst are described. The effect of the heteroatoms and a plausible mechanism are discussed. The method is operationally simple and involves low-cost starting materials affording products in good to excellent yields

DoE (Design of Experiments) Assisted Allylic Hydroxylation of Enones Catalysed by a Copper–Aluminium Mixed Oxide

The allylic hydroxylation of enones using dioxygen as the oxidant has been studied. The reaction was first examined in the absence of any catalyst, using β-ionone as a model substrate. Then a new copper–aluminium mixed oxide, Cu–Al Ox, was prepared and characterized in order to be used as a catalyst. This oxide showed good activity, and provided the corresponding γ- or ε-hydroxylated enones, starting from different α,β- or α,β,γ,δ-unsaturated ketones. In all cases, the yields were significantly improved compared to experiments run in the absence of the catalyst. The reaction was selective, and the formation of epoxides or other overoxidation products was detected only to a minor extent. The described procedure is a technically straightforward synthetic alternative to those methods described to date involving many reaction steps or toxic reagents. The reactions were optimized using design of experiments techniques (DoE)

Allylic Oxidation of Alkenes Catalyzed by a Copper−Aluminum Mixed Oxide

A strategy for the allylic oxidation of cyclic alkenes with a copper−aluminum mixed oxide as catalyst is presented. The reaction involves the treatment of an alkene with a carboxylic acid employing tert-butyl hydroperoxide as the oxidant. In all cases, the corresponding allylic esters are obtained. When L-proline is employed, the allylic alcohol or ketone is obtained. The oxidation of cyclohexene and valencene has been optimized by design of experiments (DoE) statistical methodology

Acyloxylation of Cyclic Enones: Synthesis of Densely Oxygenated Guaianolides

The α′-acyloxylation of cyclic enones with linear carboxylic acids is described. The reaction is promoted by KMnO4 in the presence of a carboxylic acid and its corresponding carboxylic anhydride. The optimization of the reaction has been carried out using the statistical methodology known as design of experiments. The optimized reaction conditions have been evaluated in terms of substrate scope and compatibility with different functional groups. The methodology has been applied to the synthesis of densely oxygenated guaianes and guaianolides

Acción del nitrato de plata sobre lactonas sesquiterpénicas cloradas

En el tratamiento de tres sustancias derivadas de la clorohyssopifolina A (III, IV y V) con gel de sílice impregnada de nitrato de plata, se obtuvieron cuatro lactonas sesquiterpénicas epoxiadas (VI, VII, VIII y IX), nuevas en la Bibliografía cuyas estructuras se determinaron por métodos espectroscópicos.Four new epoxidated sesquiterpene lactones (VI, VII, VIII and IX) were formed whwn three derivatives of chlorohyssopifalin A (III, IV and V) were treated with silica gel impregnated with silver nitrate. The structures of these new compounds were established by spectroscopic methods.Peer reviewe

Esteroquímica del anillo oxirano de la 1,10-epoxiachillina

3 págs, 1 esquema.[ES] La estereoquímica del anillo oxirano en la 1,10-epoxiachillina se ha establecido mediante transformaciones químicas y datos R.M.N.[EN] The stereochemistry of oxirane ring in 1,10-epoxyachillin has been established by chemical transformations and N.M.R. data

Subexpinnatin, a new guaianolide from Centaurea canariensis

Two sesquiterpene lactones, the new guainolide subexpinnatin and aguerin B, were isolated from the aerial part of Centaurea canariensis.Peer reviewe

Sesquiterpene lactones from Centaurea linifolia Vahl

Three new sesquiterpene lactones, linichlorins A, B, and C were isolated from the aerial parts of Centaurea linfolia Vahl and their structures were determined by physical and chemical methods. The sesquiterpene lactones chlorohyssopifolins A, B, C, D, E, aguerin B, and vahlenin were also isolated from the same plant.Trois nouvelles lactones sesquiterpániques ont été isolées a partir de Centaurea linifolia Vahl; ses structures on été deterninées par des méthodes physiques et chimiques. On a isolé aussi les lactones sesquiterpániques, chlorohyssopifolins A, B, C, D, E, aguerin B et vahlenin.Peer reviewe