Deprotonation des allylbenzenes chrometricarbonyle en milieu basique. Influence du systeme basique et du groupement chrometricarbonyle sur la regioselectivite de l'addition des derives carbonyles et sur la nature des produits isoles

Article abstract of DOI:10.1016/0022-328X(91)80262-I

Allylbenzene chromiumtricarbonyl complexes are deprotonated under several basic conditions: ^tBuOK-THF, NaH-DMF and phase transfer catalysis.The regioselectivity of the addition of carbonyl compounds on the complexed allylic anions is influenced by the nature of the cations M⁺.With M⁺ = K⁺, Na⁺, N⁺ (ⁿBu)4 the reaction of aromatic aldehydes is under thermodynamic control; only the most stable alcohols, dienes or ketones are isolated.With M⁺ = K⁺, ketones are formed by an in situ Oppenauer-Woodward oxidation.With M⁺ = Li⁺ the reaction is in great part under kinetic control.Benzaldehyde gives rise to a mixture of α and γ alcohols.With acetophenone and diethyl ketone the reaction is regiospecific.Only the linear alcohols are obtained.This result, different from that obtained in non-complexed series under similar conditions, is the consequence of the steric strain of the complexed benzenic nucleus.