A Green Approach for Efficient Synthesis ofDihydropyrano[c]chromenediones Using CuI NPs as a HeterogeneousCatalyst under Grinding

In the last few years, the use of nanosized heterogeneous catalysts in organic synthesis has proved to be useful in several scientific and technological areas. The good catalytic performance of nanosized catalysts is closely related to the activation of adsorbedcompounds and the reaction rate enhancement, easier work-up, reusability of the catalyst and the environmental friendly reaction conditions [1]. Nanosized copper iodide is one reusable Lewis acid catalyst which has revealed several catalytic activities for the synthesisof organic compounds and others [2-4]. Chromene is a prominent structural motif found in various natural and non-natural products which have been reported to show a wide spectrum of useful biological properties such as antioxidant, anticancer, antimicrobial, and etc. [5, 6].Herein we report a highly efficient and practical method for the synthesis of 4-aryl-3,4- dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones (4) via a condensation reaction of Meldrum’s acid (1), aromatic aldehydes (2), and 4-hydroxycoumarin (3) catalyzed by CuI nanoparticles (CuI NPs) under solvent-free grinding