Abstract EN:

In a first topic, we studied the oxidation of mandelic acid derivatives by Bi(III) carboxylates and by metallic bismuth under molecular oxygen. We determined the oxidation selectivity. Under our conditions, the presence of an electron-withdrawing substituent on the aromatic ring allowed the formation of the corresponding benzoic acid. For an electron-donating substituent, the reaction selectivity depended on the nature of substituent. Thus, the oxidation of p-hydroxymandelic acid afforded to p-hydroxybenzaldehyde. In contrast, with p-OMe the oxidation of the corresponding mandelic acid gave p-methoxybenzoic acid and p-anisaldehyde in a 2:1 ratio. Different mechanistic considerations are presented. The Bi(III)Bi(0) redox couple under O2 constitutes a new catalytic system for the oxidation of mandelic acids. A second topic deals with the description of a new electrochemical process for the preparation of metallic triflates and N,N- bis(trifluoromethylsulfonyl)imides. The cathodic reduction of the acid (TFSI ou triflic acid) is related to the anodic oxidation of metal. The metallic salt is formed in solution. The reactions are carried in DMF with a stainless steel or carbon fibre cathode. During the electrosynthesis a slower chemical reaction was possible for metals with a redox potential lower than -0. 7 V (NHE). With a metal which has an E0>0 V, the metallic salt generated in-situ was partly reduced in solution? In this last case, the yields of the reactions were increased by the use of nitrométhane as the solvent and platinum or gold as the cathodes. The formation of an organic salt resulting from the protonation of the solvents by the acids a=was identified. The reactivity of metallic triflates as catalysts in organic syntheses was also studied.