Lewis acid promoted reactions of ethenetricarboxylates with allenes: synthesis of indenes and gamma-lactones via conjugate addition/cyclization reaction.

Indenes are important core structures in organic chemistry. Few simple arylallenes have been used to construct indene skeletons by Friedel-Crafts reaction. Lewis acid catalyzed reaction of ethenetricarboxylates 1 and arylallenes has been examined in this study.