Synthesis of Tetrahydrobenzo[b]pyran Derivatives using SO3H–functionalized Nano-MGO-D-NH2 in Aqueous Media

In organic transformations, catalysts play a significant role, and most of these reactions are acid catalyzed. The most generally acidic catalysts are sulfuric, hydrochloric, nitric and phosphoric acids. However, corrosive properties, inability to be reused and tough separation are their drawbacks. Immobilization of organic molecules with active catalytic sites on the surface of insoluble solids such as inorganic materials, synthetic organic polymers or hybrid materials is a common way for the preparation of heterogeneous catalysts. One of the most useful heterocycles for the mild and defined incorporation of sulfonate groups into organic molecules are sultones (as cyclic sulfonate esters). Sultones behave as a sulfoalkylating agents by reacting with a wide variety of nucleophiles via carbon–oxygen bond cleavage. As green chemistry becoming a vital topic in both industrial and academic investigation in the last decades [1] the growth of environmentally benign and unpolluted synthetic procedures have become the aim of present-day organic synthesis in multicomponent reaction. Due to the diverse biological properties associated with tetrahydrobenzo[b]pyrans, there is extensive interest in the synthesis of such compounds. Tetrahydrobenzo[b]pyrans and their derivatives are an important class of heterocyclic compounds and have prominent properties such as antitumor, antibacterial, antihypertensive, hepatoprotective, cardiotonic, vasodilator and bronchodilators [2]. An efficient one-pot threecomponent procedure has been progressed for the preparation of tetrahydrobenzo[b]pyrans using SO3H–functionalized Nano-MGO-D-NH2 as a novel catalyst in aqueous media at roomtemperature, in this study. Some benefits of this methodology have been listed below: use of the reusable catalyst, easy access, short reaction times, high yields, easy work-up and use the non-toxic and green solvent.