PbWO4 nanoparticles: A robust and reusable heterogeneous catalyst for the synthesis of benzopyranopyridines under ultrasonic irradiation

An efficient four-component synthesis of benzopyranopyridines is described by one-pot condensation of salicylaldehydes, thiols and 2 equiv of malononitrile with nano-PbWO4 as a robust and reusable heterogeneous catalyst under ultrasonic irradiation. Lead tungstate (PbWO4) nanostructures have been synthesized via a sonochemical method based on the reaction between lead (II) nitrate and sodium tungstate dihydrate in an aqueous solution. Some advantages of this protocol include use of simple and readily available starting materials, rapid assembly of medicinally privileged heterocyclic molecules, reusability of the catalyst, low amount of the catalyst and application of the sonochemical methodology as an efficient technique and innocuous means of activation in synthetic chemistry.