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

Iv,N,N-dimethylhydrazones of aldehydes can be efficiently oxidized in a cat alytic way by hydrogen peroxide associated with methyltrioxorhenium (MTO) a s the catalyst to give nitriles. Elimination of dimethylhydroxylamine that is further oxidized to N-methyl-M-methylene N-oxide takes place. This nitro ne was fully characterized as such and also as its cycloaddition product wi th methylmethacrylate. This system tolerates many other functionalities and especially carbon-carbon double bonds which are not epoxidized under the p recise conditions outlined herewith. The reaction has also been extended to a few hydrazones derived from ketones: a good recovery of the ketones is a gain 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 n itrogen-nitrogen bond rupture. (C) 2000 Academie des sciences/Editions scie ntifiques et medicales Elsevier SAS.