Showing papers by "Henri Rudler published in 2000"

Copper(II)-catalyzed aerobic oxidation of indane in the presence of aldehydes: intermediate formation of hydroperoxides

Abstract: Indane reacts with oxygen, at room temperature, in the presence of isobutyraldehyde, and a copper(II) derivative (Cu(OH) 2 , CuCl 2 , Cu(TPIP) 2 ) to give a mixture of indan-1-yl hydroperoxide and indanone, together with small amounts of indanol. In the presence of Tempo or diphenylamine, as radical scavengers, no reaction takes place. Thus, no direct formation of indanol, as precursor of indanone, via metal-oxo derivatives is likely to occur. The ratio hydroperoxide/indanone is highly dependent on the nature of the transition metal in TPIP-derived complexes.

Methyltrioxorhenium-catalyzed oxidation of aldehyde and ketone N,N-dimethylhydrazones with H2O2: formation of nitriles from aldehydes and regeneration of the ketones

Abstract: N,N-dimethylhydrazones of aldehydes can be efficiently oxidized in a catalytic way by hydrogen peroxide associated with methyltrioxorhenium (MTO) as the catalyst to give nitriles. Elimination of dimethylhydroxylamine that is further oxidized to N-methyl-N-methylene N-oxide takes place. This nitrone was fully characterized as such and also as its cycloaddition product with methylmethacrylate. This system tolerates many other functionalities and especially carbon–carbon double bonds which are not epoxidized under the precise conditions outlined herewith. The reaction has also been extended to a few hydrazones derived from ketones: a good recovery of the ketones is again observed. In one case, the fate of the protecting group could also be established: as for hydrazones of aldehydes, a nitrone is formed upon the nitrogen–nitrogen bond rupture.

Single versus double nucleophilic addition of carboxylic acid enolates to anisole tricarbonyl chromium complexes with formation of arylcarboxylic acids and/or tetrahydrobenzofuran-2,5-diones: the size of the substituents on the acid makes the difference

Abstract: Potassium enolates of carboxylic acid trimethylsilyl esters, obtained upon interaction of bis(trimethylsilyl)ketene acetals with t-BuOK, react with anisole tricarbonyl chromium to give, directly upon iodine promoted oxidative demetalation, a mixture of the expected carboxylic acids and of bicyclic lactones resulting, on a formal point of view, from a double nucleophilic addition of the dianions of the carboxylic acids to the arene complexes followed by hydrolysis of labile dienol ethers. The course of the reaction was highly dependent on the nature of the starting carboxylic acid: enolates resulting from sterically crowded carboxylic acids led in preference to the lactones, whereas those originating from non-hindered acids gave mostly arylcarboxylic acids. The structures of two of these lactones have been established by X-ray diffraction studies. An intermediate dienol ether originating from the 1,2 addition of t-butyl acetic acid dianion to a double bond of anisole could be isolated and fully characterized by NMR spectroscopy. © 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS arene–tricarbonyl–chromium complexes / bis(trimethylsilyl)ketene acetals / arylcarboxylic acids / tetrahydrobenzofuran-2,5-diones

A Two-Step, Catalytic Synthesis of δ-Hydroxy-γ-lactones from Allylic Acetates and Bis(trimethylsilyl)ketene Acetals.

Abstract: Bis(trimethylsilyl) ketene acetals react successively with allylic acetates, in the presence of Pd(0) then with H2O2, in the presence of methyltrioxorhenium, to give δ-hydroxy-γ-lactones via γ-unsaturated carboxylic acids.