Sonosynthesis of pyranochromenes and biscoumarins catalyzed by Co3O4/NiO@GQDs@SO3H nanocomposite

Abstract Co3O4/NiO@GQDs@SO3H nanocatalyst has been used as an effective catalyst for the preparation of dihydropyrano[3,2-c]chromenes and biscoumarins under ultrasonic irradiations in ethanol. The catalyst has been characterized by FT-IR, XRD, SEM, EDS, BET, TGA, XPS and VSM. Atom economy, reusable catalyst, low catalyst loading, applicability to a wide range of substrates, high yields of products, and applying the sonochemical methodology as an efficient method and innocuous means of activation in synthetic chemistry for the preparation of medicinally privileged heterocyclic molecules are some of the substantial features of this method. The present catalytic procedure is extensible to a wide diversity of substrates for the synthesis of a variety-oriented library of pyranochromene and biscoumarins. The ultrasound approach decreases times, increases yields of products by creating the activation energy in micro surroundings. Meanwhile, this recoverable catalyst will provide a regular platform for heterogeneous catalysis, green chemistry, and environmentally benign protocols in the near future. Graphical Abstract