Acid-Mediated Cascade Cyclization Pathway to Indeno[2,1- c ]chromen-6(7 H )-ones.

Developing mild and effective synthetic strategies for producing significant molecules starting from readily available starting materials is indispensable in organic synthesis. Herein, we present a triflic acid-driven dual cyclization pathway to produce functionalized indeno[2,1- c ]chromen-6(7 H )-ones from simple 2-formyl (or 2-acyl) cinnamate esters and phenols. Notably, this protocol enabled the construction of two C-C bonds and one C-O bond under metal-free reaction conditions via the activation of the unreactive ester moiety in a single pot. The isolation of intermediate indenol-ester might suggest self-intramolecular cycloaddition by the proximate double bond of the enoate ester with the o -carbonyl moiety, followed by an electrophilic attack with phenol and a subsequent cyclocondensation pathway. In addition, the photophysical properties have also been examined.