Old Drawback on Azlactone Formation Revealed by a Combination of Theoretical and Experimental Studies

New insights into the formation of azlactone heterocycles bearing different substituents are hereby presented. The sum of both kinetic and thermodynamic factors contributes for the formation of 2-alkyl or 2-aryl substituted azlactones, while the cyclization of 2-alcoxy azlactones is less favored. These results are in perfect accordance with experimental observations obtained by infrared (IR) and electrospray ionization mass spectrometry (ESI(+)-MS) of the crude reaction mixture.本文报道了对带有不同取代基的恶唑酮（azlactone）杂环形成过程的全新认知。动力学与热力学因素的共同作用促成了2-烷基取代或2-芳基取代恶唑酮的生成，而2-烷氧基取代恶唑酮的环化过程则较难发生。上述结果与通过红外光谱（IR）和电喷雾电离质谱（ESI(+)-MS）对粗反应混合物进行表征得到的实验观测结果完全吻合。