Jacques Berlan

Organocopper conjugate addition reaction in the presence of trimethylchlorosilane

Abstract In the presence of TMSCl, the conjugate addition of organocuprates to various α, β-unsaturated esters, amides, ketones and nitriles is greatly improved. The reaction is faster, the yields are very high and the reaction is very clean.

Synthese organique sous champ microondes : premier exemple d'activation specifique en phase homogene

Resume The rate of several Diels-Alder reactions under conventional or microwave heating are compared at the same bulk temperature. This afford the first evidence for a specific activating effect of microwaves under homogeneous conditions.

Oxidation of phenol in wastewater by sonoelectrochemistry

Abstract Mass transfer was investigated in ultrasonic reactors by means of the electrochemical method (feri-ferro-cyanide couple, under diffusion limitations). This method allowed for the determination of the active zones in the reactor. The oxidation of a model pollutant, phenol, has been carried out in the previously screened reactor, with ultrasound alone and with ultrasound associated with electrolysis. With a 20 kHz sonication, the electrochemical oxidation of phenol in NaCl media allows the conversion of 75% of initial phenol within 10 minutes of treatment. However a toxic intermediate, p.quinone was formed. At 500 kHz a conversion of 95% of the initial phenol was obtained within the same treatment time, and final products of degradation were acetic and chloroacrylic acids.

Microwave heating of organic solvents: Thermal effects and field modelling

Abstract Superheating of ethyl and methyl alcohols (under microwave in a monomode cavity has been studied), in connection with field modelling. Non-even field distribution can seems to induce a lack of reproducibility in measurements and superheating.

Electrochemical determination of the active zones in a high-frequency ultrasonic reactor

In order to design a new reactor based on sonoelectrochemical technology for processes of wastewater treatment, mass transfer is studied in a high-frequency (560 kHz) ultrasonic reactor. The determination of the active zones is of particular interest because it allows to locate the electrodes where mass transfer is highest. The determination of the mass-transfer coefficient was achieved by measuring the diffusion current obtained in the electrochemical reduction of potassium ferricyanide. Mean mass-transfer coefficients kd are calculated at different points throughout the reactor and a spatial distribution of kd is obtained which represents the active zones of the reactor. This spatial distribution is in good agreement with the one obtained recently by chemiluminescence measurements and confirms the difference existing between the spatial distribution obtained by sonication at low frequency (20 kHz) and high frequency (500 kHz) ultrasound.

AN ORIGINAL MICROWAVE-ULTRASOUND COMBINED REACTOR SUITABLE FOR ORGANIC SYNTHESIS : APPLICATION TO PYROLYSIS AND ESTERIFICATION

An original microwave-ultrasound combined reactor has been developed. Its application to organic synthesis has been shown by two examples of chemical reactions where increases in yield were demonstrated: pyrolysis and esterification.

‘Dry’ hydrolysis of nitriles effected by microwave heating

The preparation of carboxylic acids from their corresponding nitriles by a ‘dry hydrolysis’ with dicarboxylic acids, in the absence of solvent, has been investigated. The reaction proceeds very slowly at atmospheric pressure, but high yields can be obtained in much shorter reaction times under pressure. The mechanism of the reaction has been studied and its rate constant and activation energy determined in the case of a model reaction (preparation of phenylacetic acid from benzyl cyanide with phthalic acid) under both microwave and conventional heating. No ‘microwave kinetic effect’ has been detected, but at high temperatures microwave heating gives better yields and selectivities.

Influence of ultrasound power on the alkylation of phenylacetonitrile under solid-liquid phase transfer catalysis conditions.

The influence of ultrasound power on the C-alkylation of phenylacetonitrile by ethyl bromide was studied under solid-liquid phase transfer catalysis in the presence of potassium hydroxide and tetrabutylammonium hydrogenosulfate. Experimental results are reported on the influence of the ultrasonic power on the yields. The optimum efficiency of ultrasounds is determined and the way in which ultrasound power may affect the yields is discussed.

Application of ultrasound technology to electroorganic synthesis: Reduction of acetophenone

Abstract Electroreduction of acetophenone in an undivided cell was chosen as a model reaction to investigate the use of ultrasonication in organic electrosynthesis. The reaction was carried out in aqueous medium (water–methanol), at neutral pH and at a cadmium or zinc cathode. Electrochemical reduction of acetophenone yields alcohol through a bielectronic transfer and pinacol through a monoelectronic transfer. Operating conditions permit to modify the reduction state of the reactant. On a cadmium cathode, the major product is the alcohol whereas on a zinc cathode, the pinacol is rather obtained. The ultrasonic activation has been studied as regards the faradaic yield and the chemical selectivity. This work puts into evidence the interest of ultrasonication for electroorganic synthesis processes often submitted to passivation phenomena.

Addition des cuprates aux systemes alleniques actives: Reactivite des intermediaires

The addition of lithium dimethylcuprate to allenic phosphine oxide or carbonyl compounds leads, via I-2 addition to the activated carbon—carbon double bond, to stable organocopper(I) species including methyl and functional allyl groups. We have studied the reactivity of such species with two models. In their reaction with an electrophile they transfer, most often specifically, either the methyl or the allyl group, and in this latter case the reaction is also most often stereo- and regio-selective. At this time it is however difficult to rationalise these observations but some interesting applications may be envisaged for synthetic purposes.