Humic Acid as a Recyclable Green Catalyst for the Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones in Water

A green and highly efficient protocol has been developed for the synthesis of 2,3-dihydroquinazolin-4(1 H )-ones via the cyclocondensation of 2-aminobenzamide with various aldehydes or ketones. The reactions proceed smoothly at room temperature in water, utilizing a catalytic amount of humic acid as an environmentally benign, cost-effective, and highly recyclable heterogeneous catalyst. This operational method offers several key advantages, including the use of an aqueous medium, mild operating conditions, excellent product yields, simple workup procedures, and seamless scalability to a gram scale.