This paper is dedicated to Professor Habib Firouzabadi for his great contribution in organic chemistry on the occasion of his 6S th birthday and his honourable retirement.The effect of a series of metal oxides on synthesis of diethyl l-hydroxyphosphonates under solvent free condition was studied and the results showed that calcium oxide was the most efficient reagent than the others for preparation of the title compounds.

In this study, mesoporous NiFe2O4@SiO2@KIT‐6 core‐shell nanoparticles with magnetic properties were synthesized. Functionalization of the KIT‐6 shell with chlorosulfonic acid afforded the NiFe2O4@SiO2@KIT‐6‐SO3H hybrid material. Sulfonated Caspian Sea sand, on the other hand, was obtained by silica enrichment with hydrochloric acid followed by –SO3H functionalization with chlorosulfonic acid. Efficiency of these –SO3H functionalized solid acids were compared in the synthesis of biologically important 1,4‐dihydropyridines and 3,4‐dihydropyrimidin‐2(1H)‐ones via corresponding multicomponent reactions and both resulted in good to excellent yields of the desired products under very mild conditions. It was found that the amount of acidic groups (12.58 mmol SO3H g−1 of NiFe2O4@SiO2@KIT‐6‐SO3H vs. 1.02 mmol SO3H g−1 of the sulfonated sand) can be related to BET surface area of the catalysts (160 m2/g vs. 12 m2/g). Although much higher amounts of the sulfonated sand was necessary in comparison with NiFe2O4@SiO2@KIT‐6‐SO3H to obtain satisfactory yields of the organic products, the easy procurement method and the abundance of raw materials needed to make sulfonated Caspian Sea sand was an indisputable advantage. Both catalysts showed good recyclability along with negligible decrease in their efficiency over five periods.