Microwave assisted the synthesis of benzo[a]pyrano-[2,3-c]phenazine derivatives catalyzed by Multisulfonate hyperbranched polyglycerol functionalized graphene oxide as a novel and reusable catalyst

In recent years, designs of multi-component reactions (MCRs) because of their advantages in comparison with multi-step reactions according to environmental and economic considerations have received significant attention for the synthesis of biologically interesting compounds [1]. Also, microwave -assisted organic synthesis applied as an eco-friendly and powerful synthetic approach to accelerate organic reactions. Recently, carbon based nanostructures such as graphene oxide have used as substrate for polymer matrices [2]. Hyperbranched polyglycerols belong to a group of macromolecules have attracted considerable attention over the past few years due to their unique molecular structure and properties [3]. A class of hyperbranched polymers are the aliphatic polyether polyols named polyglycerol with tree-like structure that have wide range of new properties, and thus a greater area of applications [4]. Phenazines are nitrogen-containing heterocycles that exist in natural and synthetic products .They are structural components of diverse kinds of bacteria species. They have been demonstrated various pharmaceutical activities. Moreover, chromenes as an important class of compounds have been showed remarkable effects as pharmaceuticals such as antifungal and antimicrobial activities. Although molecules with phenazines and chromenes moieties have attracted a lot of attention in drug discovery but functionalized benzo[a]pyrano[2,3-c]phenazine derivatives have seldom been described. Herein, we would like to report the synthesis of multisulfonate hyperbranched polyglycerol modified graphene oxide (GO-HPG-SO3H) as highly efficient and reusable catalysts for the preparation of benzo[a]pyrano[2,3-c]phenazine derivatives via a four-component reaction of 2-hydroxynaphthalene-1,4- dione, o-phenylenediamine, aldehydes, and malononitrile under Microwave irradiation.