Reagent and method useful for splitting a protected function, in the event of organic synthesis by an allyl group with the latter. The reagent is characterized by having a) a solvent system; b) a catalyst comprising at least one element from column VIII of the periodic table of elements, said element being coordinated by at least one coordinating agent soluble in the said solvent system; and c) a compound at least partially soluble in said solvent system and carrying at least one nucleophilic function. Application in organic synthesis.