Microwave irradiation leads to a considerable improvement of the cyclocondensation between anthranilic acid and lactim ethers derived from piperazine-2,5-diones in terms of reaction times, yields, and stereocenter integrity. This reaction has been used to prepare some derivatives of the pyrazino[2,1-b]quinazoline-3,6-dione system present in many quinazoline alkaloids. It could also be applied to the synthesis of compounds containing the complete hexacyclic ring system of the anti-MDR natural product N-acetylardeemin, and other comprising the pentacyclic framework of circumdatin E. The microwave-assisted reaction was also much better than the thermal one when applied to a bis-lactim ether, leading to the corresponding pentacyclic pyrazino[2,1-b:5,4-b′]diquinazoline-8,16-dione in excellent yield.
微波辐照显著改善了
邻氨基苯甲酸与来自
哌嗪-2,5-二
酮的乳
酰亚胺醚之间的环加成反应,在反应时间、产率和立体中心完整性方面均有显著提升。该反应已被用于制备多种
喹唑啉生物碱中存在的
吡嗪并[2,1-b]
喹唑啉-3,6-二
酮系统的衍
生物。它还可以应用于合成含有抗多药耐药
天然产物N-乙酰基阿德米宁的完整六环体系化合物,以及其他包含circumdatin E的五环框架的化合物。微波辅助反应在应用于双乳
酰亚胺醚时也比热反应更为高效,得到了对应的五环
吡嗪并[2,1-b:5,4-b′]双
喹唑啉-8,16-二
酮,产率极佳。