Abstract
A simple, cost-effective method under environmentally benign conditions is a very important concept for the preparation of 2,3-dihydroquinazolin-4(1H)-one derivatives. The present work describes an efficient and eco-friendly protocol for the synthesis of 2-amino-N-(2-substituted-ethyl)benzamide and 3-substituted-2,3-dihydroquinazolin-4(1H)-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 (1H and 13C), elemental analysis, and LC-MS confirmed the structures of all compounds. X-ray crystallography further confirmed the structure of the intermediate 2-amino-N-(2-substituted-ethyl)benzamide 3a. The molecular structure of 3a was monoclinic crystal, with P21/c, a = 13.6879 (11) Å, b = 10.2118 (9) Å, c = 9.7884 (9) Å, β = 105.068 (7)°, V = 1321.2 (2) Å3, and Z = 4.
Highlights
The dihydroquinazolinone moiety is present in numerous biologically active molecules with various potential therapeutic effects [1,2,3,4,5,6,7,8,9]
In view of the increasingly widespread applications of dihydroquinazolinone derivatives, many researchers have made great effort to develop these types of compounds using different synthetic methodologies [8,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24], such as by using TiO2 nanoparticles
NPs) as a catalyst for the synthesis of 2,3-disubstituted dihydroquinazolin-4(1H)-one derivatives [25]; a metal reduction–condensative cyclization strategy [26]; a three-component reaction of isatoic anhydride with amine and 2-formyl benzoic acid in the presence of montmorillonite K10 as a catalyst [27]; ultrasound irradiation catalyzed by dodecylbenzenesulfonic acid [28]; microwave irradiation in the presence of Amberlyst-15 [29] or Cu-CNTs [30]; and condensation of isatoic anhydride, amine, or ammonium salts with aldehydes or ketones in the presence of p-toluenesulfonic acid [31], citric acid [32], or silica bonded with different acids [33,34,35]
Summary
The dihydroquinazolinone moiety is present in numerous biologically active molecules with various potential therapeutic effects [1,2,3,4,5,6,7,8,9]. In view of the increasingly widespread applications of dihydroquinazolinone derivatives, many researchers have made great effort to develop these types of compounds using different synthetic methodologies [8,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24], such as by using TiO2 nanoparticles NPs) as a catalyst for the synthesis of 2,3-disubstituted dihydroquinazolin-4(1H)-one derivatives [25];. 24, 4052 under conventional heating or microwave irradiation (MWI) in the presence of methanol as a solvent and K2CO3 as a catalyst to afford the new 2,3-dihydroquinazolin-4(1H)-one derivatives. We report an efficient and eco-friendly protocol for the synthesis of 2-amino-N-(2substituted-ethyl)benzamide from isatoic anhydride using 2-methyltetrahydrofuran (2-MeTHF), which has previously been promoted as an eco-friendly alternative solvent to tetrahydrofuran (THF) [36,37,38].
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