Microwave-Assisted Direct Synthesis of 2-Substituted Benzoxazoles from Carboxylic Acids under Catalyst and Solvent-Free Conditions
作者:Asit K. Chakraborti、Raj Kumar、C. Selvam、Gurmeet Kaur
DOI:10.1055/s-2005-868509
日期:——
A direct coupling of carboxylic acids with 2-aminophenol under microwave irradiation has been achieved leading to the synthesis of 2-substituted benzoxazoles under metal and solvent-free conditions. Aliphatic, aromatic and heteroaromatic carboxylic acids provide good yields. Benzoxazole formation takes place in the presence of chloro, methoxy, phenoxy, thiophenoxy, and α,β-unsaturated functionalities. In the case of dicarboxylic acids, the reaction proceeds via the formation of the corresponding anhydride with predominant formation of the mono-benzoxazole.
在微波辐射下,羧酸与2-氨基苯酚直接耦合,实现了无金属和溶剂条件下的2-取代苯并恶唑合成。脂肪族、芳香族和杂芳香族羧酸均可提供良好的产率。苯并恶唑的形成在氯、甲氧基、苯氧基、噻吩氧基和α,β-不饱和功能团的存在下发生。对于二元羧酸,反应通过形成相应的酸酐进行,主要生成单苯并恶唑。