The mechanochemical solvent-free synthesis of indenones from aromatic carboxylic acids and alkynes was achieved through triflic anhydride (Tf2O)-induced cyclization reaction. A variety of indenones including a bioactive PPARγ agonist were obtained in up to 90% yield at room temperature. The present protocol has the advantages of mild reaction conditions, high reaction efficiency, and feasibility of scalable synthesis, providing a facile and sustainable route to diverse indenones.