TFA-catalyzed ring transformation of 4-hydroxycyclobutenone: A simple and general route for preparation of 3-substituted 4-aminofuran-2(5H )-ones †
作者:Jie Wang、Xin Jiang、Ming Chen、Zongming Ge、Yuefei Hu、Hongwen Hu
DOI:10.1039/b004654j
日期:——
positions, respectively, to yield 4-substituted 3-aminocyclobutene-1,2-diones 14. Reduction of compounds 14 with NaBH4 yield 2-substituted 3-amino-4-hydroxycyclobutenones 15 in high yields. By ring transformation of products 15 catalyzed by TFA, a simple and general route for the preparation of 3-substituted 4-aminofuran-2(5H)-ones 4 is developed. A two-step mechanism is proposed to describe the ring
按照3,4-二异丙氧基环丁烯-1,2-二酮11的烷基化和胺化的便利顺序,可以轻松地实现三个典型的取代基(H,n-Bu和Ph)和三个典型的氨基(未取代,伯和仲)分别引入其C-3和C-4位置,以产生4-取代的3-氨基环丁烯-1,2-二酮14。用NaBH 4还原化合物14可高产率地产生2-取代的3-氨基-4-羟基环丁烯酮15。通过TFA催化的产物15的环转化,是制备3-取代的4-氨基呋喃-2(5 H)-ones 4的简单且通用的方法4被开发。提出了两步机制来描述烯酮15的环转化。实验结果表明,对二甲苯的回流过程对于15的初始热电开环以产生中间体羟基烯酮16a和16b至关重要。然后将它们在TFA存在下内酯化,以51-94%的收率得到呋喃酮4。