Superacid Mediated Intramolecular Condensation: Facile Synthesis of Indenones and Indanones

Superacid promoted intramolecular acylation of simple cinnamic acid esters for the synthesis of indenones is presented. Interestingly, in all resulted indenones, the olefin bond is rearranged to exo position of the five membered rings. Significantly, the method is further applied to the synthesis indanones via the formation of two C-C bonds by in-situ treatment of indenones with an external arene in one-pot. Most importantly, the present sequential method for the synthesis of indanones is advantageous, as it limits even more electron rich external arenes only to the Friedel-Crafts alkylation. This is not possible by the previous reports wherein both cinnamic acid ester and the external arene treated together in the presence of an acid, wherein relatively more reactive arene is preferred to facilitate acylation ste