由α-氰基肉桂酸乙酯/N-溴代苯甲酰胺合成2-噁唑啉衍生物

作为重要的杂环化合物,合成新的2-噁唑啉衍生物以及发展其新的合成方法具有重要意义,为此以α-氰基肉桂酸乙酯衍生物为底物,以N-溴苯甲酰胺为反应试剂,在无水碳酸钠(相对于底物3为110%摩尔分数)促进下,在丙酮溶剂中,室温下,建立了合成相应2-噁唑啉衍生物的新方法,共合成了11个新化合物,其结构由核磁共振波谱仪(~1H NMR,~(13)C NMR)和高分辨质谱(HRMS)确认。结果显示,各种α-氰基肉桂酸乙酯衍生物(3a~3k)可被顺利的转化成相应的2-噁唑啉衍生物(5a~5k)。在室温下,丙酮作溶剂,以Na_2CO_3为促进剂时,相应产物的最高收率可达90%。不仅α-氰基肉桂酸乙酯衍生物(3)可被用作该反应的底物,而且α-乙氧甲酰基肉桂酸乙酯(6)也适用于该反应。实验结果还证明,除了N-溴代苯甲酰胺外,N-溴代对硝基苯甲酰胺(8)及N-溴代乙酰胺(9)也适用该反应,证明该方法具有广泛的适应性。根据实验结果,提出了可能的反应机理,该机理支持了形成2-噁唑啉衍生物的区域选择性。

Synthesis of 2-Oxazoline Derivatives from Ethyl α-Cyanocinnamate Derivatives and N-Bromobenzamide

2-Oxazoline derivative belongs to an important class of heterocyclic compounds, new synthetic method and new 2-oxazoline derivatives are eagerly desired. In order to develop a new protocol for the synthesis of deferent structural 2-oxazoline derivatives, a method from ethyl α-cyanocinnamate derivatives and N-bromobenzamide has been explored. The structures of all eleven synthesized products were confirmed by proton nuclear magnetic resonance spectroscopy(¹H NMR), and mass spectrometry(MS). The results show that a series of ethyl α-cyanocinnamate derivatives(3a~3k) can be smoothly converted into corresponding 2-oxazoline derivatives(5a~5k). When Na₂CO₃ was used as the promoter in acetone at room temperature, the corresponding products were obtained in high yield(up to 90%). Not only can ethyl α-cyanocinnamate derivatives be used as substrate, but also ethyl α-carbethoxy-cyanocinnamate(6) can be employed as the substrate, too. Experiment results indicate that N-bromo-p-nitrobenzamide(8) and N-bromoacetamide(9) can tolerate this reaction except N-bromobenzamide(4). Above results indicate that the easy and efficient protocol has application in a large scope of electron-deficient olefins and N-bromoamide. A possible mechanism was proposed which can explain well the full regiospecificity of the reaction.