H₃PW₁₂O₄₀@nano‐ZnO: An efficient, recyclable, and eco‐friendly catalyst for the green synthesis of novel benzo[a]pyrimido[5′,4′:5,6]pyrano[2,3‐c]phenazines via sequential multicomponent reactions under microwave irradiation

Abstract

A simple and efficient single‐pot synthesis of novel heteroaryl‐substititued benzo[a]pyrimido[5′,4′:5,6]pyrano[2,3‐c]phenazines has been developed via initial Knoevenagel, subsequent Michael, and final heterocyclization reactions of 2‐hydroxynaphthalene‐1,4‐dione, o‐phenylenediamine, aromatic aldehydes, and barbituric acid in the presence of H3PW12O40@nano‐ZnO as a recyclable heterogeneous catalyst in EtOH under microwave irradiation (MWI). This sequential green process with several advantages, such as operational simplicity, high yields, low cost, easy handling, eco‐friendliness and reusability of the catalyst, absence of any tedious work‐up or purification, and avoidance of hazardous or toxic reagents/catalysts/solvents, opens an effective and convenient way to pyrano‐functionalized benzophenazine systems, which are promising compounds for different biomedical applications.

A review on lawsone-based benzo[a]phenazin-5-ol: synthetic approaches and reactions

“…Subsequent Michael addition of the o -QM with barbituric acid, followed by cyclization and dehydration leads to the formation of the desired product 81. 60 …”

One‐pot synthesis of 3‐(sulfonyl)‐5,6,7,8‐tetrahydro‐4H‐pyrano[3,2‐c]pyridines through a cascade Michael/cyclization reaction

“…With the spirit of sustainable development taking root in all aspects of life, green chemistry arose at a historic moment in the 1990s, gaining more and more interest, such as the design of safer chemicals and processes . The so‐called “multicomponent reactions (MCRs)” can reflect this spirit due to their features, such as superior atom economy, higher chemical yield, fewer by‐products, simpler operation and equipment, lower costs and time and energy consumption, and other environmentally benign criteria . More importantly, MCRs have emerged as an important tool in the fast and convergent synthesis of valuable compound libraries with structural complexity and molecular diversity.…”

“…[2] The so-called "multicomponent reactions (MCRs)" can reflect this spirit due to their features, such as superior atom economy, higher chemical yield, fewer by-products, simpler operation and equipment, lower costs and time and energy consumption, and other environmentally benign criteria. [3][4][5] More importantly, MCRs have emerged as an important tool in the fast and convergent synthesis of valuable compound libraries with structural complexity and molecular diversity.…”

Green synthesis of new thiouracilodepsipeptides in ionic liquid: One‐pot four‐component reaction of isocyanides

“…[1,2] In these reactions, one product is made in a single process from three or more reactant molecules with high atom-economy [3] and multiple-bond-forming efficiency. MCRs, by reason of their efficiency, simple procedures, important benefits over conservative linear-type syntheses, and facile execution, are some of the best synthesis tools in combinatorial chemistry.…”