Sur le role fondamental du cation alcalin dans les reductions par les hydrures metalliques—utilisation de coordinats macrocycliques—IV : Regioselectivite et reduction des enones conjuguees

The competition between 1,2 and 1,4-addition in the metal hydride reduction of conjugated cyclohexenones and cyclopentenones in aprotic media is affected by solvent, nature of cation (Li⁺ or Na⁺), and of anion (AlH₄^? or BH₄^?). In protic media, effects of salt concentration, and the nature of the salt are observed. Three competitive reaction pathways are proposed to account for the results and methods for the selective reduction of conjugated enones are proposed. Some reactions were run free of alkaline cation by use of macrocyclic ligands.