An efficient and green synthesis of 2‐phenylquinazolin‐4(3H)‐ones using Brønsted acidic ionic liquid grafted onto silica

Abstract

BACKGROUND The synthesis of 2‐phenylquinazolin‐4(3H)‐ones has been studied extensively, yet previous synthetic routes involved unrecyclable catalysts, toxic organic solvents and an expensive purification step with column chromatography. The current study reports on the preparation of 2‐phenylquinazolin‐4(3H)‐ones from recyclable Brønsted acidic ionic liquid grafted onto silica. RESULTS 1‐Methyl‐1‐(4‐sulfobutyl)pyrrolidinium hydrogen sulfate supported onto silica gel (MSPHS@SiO2) was prepared via a simple process. This material was demonstrated as an effective recyclable catalyst for the preparation of 2‐phenylquinazolin‐4(3H)‐ones through the cyclization of 2‐aminobenzamide and aldehydes. The optimized conditions were MSPHS@SiO2 (30 mol%), TBHP (2 mmol), EtOH:H2O (15 mL, 1:2) at 120 °C for 24 h. A wide range of 2‐phenylquinazolin‐4(3H)‐ones were obtained in 34.2–92.5% yields via simple recrystallization. The catalyst could be recycled and a plausible mechanism is proposed. CONCLUSION MSPHS@SiO2 is an efficient and recyclable heterogeneous catalyst for the synthesis of 2‐phenylquinazolin‐4(3H)‐ones from readily available and low‐cost starting materials. © 2022 Society of Chemical Industry (SCI).