Versatile and Sustainable Approach to Access Biologically Relevant Chromeno[2,3-b]pyridine and Benzylpyrazolyl Coumarin Derivatives Using Graphitic Carbon Nitride as a Reusable Heterogeneous Catalyst

Abstract

Herein, the synthesis of graphitic carbon nitride (g-C3N4) via the simple heating of cheap and readily available urea as the starting material has been reported. The catalytic activity of the prepared g-C3N4 was investigated for the synthesis of chromeno[2,3-b]pyridine and benzylpyrazolyl coumarin derivatives in an ethanol medium. The reactions were performed under mild conditions to achieve widely functionalized target products in a one-pot operation. The as-synthesized g-C3N4, being a heterogeneous catalyst, demonstrates excellent recyclability up to the 5th consecutive run without a significant decrease in its catalytic activity and yield of the product. A gram-scale reaction was performed to demonstrate the industrial applications of the present protocol. The green chemistry metrics such as environmental factor (E-factor), atom economy (AE), carbon efficiency (CE), and reaction mass efficiency (RME) were calculated and found to be very close to the ideal values. Additionally, operation simplicity, wide substrate scope, easy reusability of the catalyst, and avoidance of metal contamination in the products drive the process toward green and sustainable development.

Bis(2-cyanoacetamide) in Heterocyclic Synthesis: Synthesis of Some Bis[2-oxopyridine, 2-iminochromene, Chromeno[3,4-c]pyridine, Benzochromeno[3,4-c]pyridine] Derivatives

“…Functionalized chromenes are widely used to synthesize promising compounds in medicinal chemistry [28][29][30][31][32][33][34][35] . Wide-ranging pharmacological activity, such as antibacterial 36 , anti-inflammatory 37 , antimicrobial 38 , anti-proliferative 39 , hypotensive 40 , and antirheumatic 41 properties, have been reported for derivatives of chromenopyridine. Many natural and pharmaceutical compounds contain fused chromenes like chromenopyridines.…”

CSA@g-C3N4 as a novel, robust and efficient catalyst with excellent performance for the synthesis of 4H-chromenes derivatives

“…Multicomponent reactions (MCR) provision deep knowledge regarding 4H-chromene formation. Furthermore, considerable catalytic schemes have evolved over recent years for the multicomponent synthesis of 4H-chromene derivatives, including RGO-SO 3 H 59 , GO/α-Fe 2 O 3 /CuL 60 , MNPs@Cu 61 , g-C 3 N 4 62 , Pd@g-C 3 N 4 63 , CaMgFe 2 O 4 64 , morpholine 65 , CAEDA 66 , mica/Fe 3 O 4 67 , amino grafted MOFs 68 , DABCO 69 , Fe 3 O 4 @Sal@Cu 70 , Fe 3 O 4 @GO-NH 71 , KCC-1@NH 2 72 , Nano-SiO 2 73 , SnO 2 NPs 74 , Ag 2 O/GO/TiO 2 75 , and borax 76 . Yet, there are several drawbacks concerning plenty of expressed catalysts, including environmental contamination, high price, challenging catalyst removal, and requiring coarse reaction conditions.…”