The Selective Claisen and Dieckmann Ester Condensations Promoted by Dichlorobis(trifluoromethanesulfonato)titanium(IV)

Inter and intramolecular condensations (the Claisen and the Dieckmann condensations) between ester functions have been performed by the combined use of dichlorobis(trifluoromethanesulfonato)titanium(IV) (= dichlorobis(triflato)titanium(IV)) and tertiary amine under mild reaction conditions. These results led to the development of the selective (crossed) Claisen and Dieckmann ester condensation between methoxymethyl ester and methyl ester, in that, dichlorobis(triflato)titanium(IV) contribute to control the direction of the reaction.