Lewis acid-promoted cyclization/halogenation of allenyl ethenetricarboxylates and the corresponding amides: stereoselective synthesis of haloalkenyl five-membered heterocycles

Abstract

Lewis acid-promoted intramolecular reactions of allenyl ethenetricarboxylates and the corresponding amides have been examined. Reactions of allenyl ethenetricarboxylates and the amides with Lewis acids such as AlCl₃, AlBr₃ and ZnX₂ (X = Cl, Br, I) gave 3,4-trans haloalkenyl five-membered heterocycles stereoselectively. The stereochemistry was determined by NOE experiments and reduction of the cyclized products. Various transformations of the haloalkenyl functionalized cyclic compounds have also been performed.