Visible light-mediated synthesis of quinazolinones from benzyl bromides and 2-aminobenzamides without using any photocatalyst or additive.

Abstract

This paper reports a novel method for the visible-light-mediated synthesis of quinazolinones from the reaction of benzyl bromides with 2-aminobenzamides. The reaction proceeded efficiently at room temperature upon irradiation with an 18 W blue light-emitting diode in air without photocatalysts or additives. By varying the solvent type, substrate molar ratio, and reaction time, the optimal reaction conditions, including the use of methanol solvent, room temperature, and reaction time of 28 h, were identified. Under these conditions, various quinazolinones were obtained using 18 substrates, with the highest yield of 93%. To determine the industrial value of the proposed method, a scale-up reaction was performed and 80% product yield was achieved. Mechanistic studies revealed that the reaction likely proceeded via a radical pathway and that the hydrogen bromide by-product generated during the first step of the reaction of benzyl bromide with 2-aminobenzamide promoted the subsequent step.