Action des reactifs de grignard sur les dithioesters : Addition carbophile d'organomagnesiens insatures. synthese de cetones β-ethyleniques

Reactions of allyl, benzyl, propargyl and vinyl Grignard reagents with methyl dithioacetate give dithioacetals (or hemidithioacetals) resulting from a carbophilic addition process. Reactions with various allylic organomagnesium compounds always involve an “inversion” of the allylic chain and direct carbophilic addition, rather than initial thiophilic addition followed by [2.3] sigmatropic shift. Three methods for the synthesis of β-unsaturated ketones are described, showing the potential synthetic uses of the reactions of Grignard reagents with dithioesters.