A Simple, Efficient, and Eco-Friendly Method for the Preparation of 3-Substituted-2,3-dihydroquinazolin-4(1)-one Derivatives.

A simple, cost-effective method under environmentally benign conditions is a very important concept for the preparation of 2,3-dihydroquinazolin-4(1)-one derivatives. The present work describes an efficient and eco-friendly protocol for the synthesis of 2-amino--(2-substituted-ethyl)benzamide and 3-substituted-2,3-dihydroquinazolin-4(1)-one derivatives. The novel feature of this protocol is the use of 2-methyl tetrahydrofuran (2-MeTHF) as an eco-friendly alternative solvent to tetrahydrofuran (THF) in the first step. In the second step, methanol in the presence of potassium carbonate as a catalyst was used under conventional heating or microwave irradiation, which provided an eco-friendly method to afford the target products in excellent yields and purities. NMR (H and C), elemental analysis, and LC-MS confirmed the structures of all compounds. X-ray crystallography further confirmed the structure of the intermediate 2-amino--(2-substituted-ethyl)benzamide . The molecular structure of was monoclinic crystal, with 21/, = 13.6879 (11) Å, 10.2118 (9) Å, = 9.7884 (9) Å, = 105.068 (7)°, = 1321.2 (2) Å3, and = 4.