Sustainable parts‐per‐million level catalysis with Fe^III: One‐pot cascade synthesis of 2,3‐dihydroquinazolin‐4(1<i>H</i>)‐ones in water

Abstract

A silica‐supported iron complex has been identified as a highly active and reusable catalyst for the synthesis of medicinally important 2,3‐dihydroquinazolin‐4(1 H )‐ones. The catalyst was fully characterized by various spectroscopic analyses such as Fourier‐transform infrared spectroscopy (FT‐IR), ultraviolet‐visible (UV–VIS), scanning electron microscopy (SEM), scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM–EDX), energy‐dispersive spectroscopy (EDS) mapping, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), inductively coupled plasma atomic emission spectroscopy (ICP‐AES), elemental analysis, Brunauer–Emmett–Teller (BET) isotherm and thermogravimetric analysis (TGA) analysis. A diverse library of 2,3‐dihydroquinazolin‐4(1 H )‐ones including some new analogues were successfully synthesized in good to excellent yields with parts‐per‐million (ppm) levels of Fe using water as a solvent. The active catalyst has high turnover number (TON) and turnover frequency (TOF) at the optimized condition, which were 30,087 and 30,087 h −1 , respectively. Ppm level catalysis, wide substrate scope, shorter reaction time, reusability of the catalyst, green solvent media and gram‐scale synthesis make this protocol eco‐friendly and sustainable.