Preparation of 3-hydroxy-2,3-dialkoxy-2-phenylchroman-4-ones and 3,3-dihydroxy-2-alkoxy-2-phenylchroman-4-ones by oxidation of 3-hydroxyflavone with copper(II) bromide: Structure, reactivity and characterization
作者:Elizabeth M. Beasley、Joseph G. Bazemore、Anthony Petrillo、Clifford W. Padgett、Will E. Lynch、Brandon Quillian
DOI:10.1016/j.ica.2020.119855
日期:2020.11
hydrates (2, 4, and 6) as well as the single crystal X-ray structures of 1–4 & 6. While the hemiacetals were shown to be kinetically accessible, the hydrates were thermodynamically preferred. The single X-ray structures of compounds 1–4 & 6 reveals the alkoxy groups occupying the axial position of the coumarin ring, which is surmised to be the source of the instability of the hemiacetals. As a result of the
摘要3-羟基黄酮与溴化铜(II)在各种醇(乙醇,异丙醇和甲醇)中的反应生成了它们各自的3-羟基-2,3-二烷氧基-2-苯基苯并四氢呋喃酮(半缩醛)的混合物和3,3-二羟基-2-烷氧基-2-苯基苯并吡喃-4-酮(水合物)。在本文中,我们报告了三种半缩醛(1、3和5)和三种水合物(2、4和6)以及1-4和6的单晶X射线结构的合成,反应性和表征。半缩醛显示出动力学上可及的,水合物在热力学上是优选的。化合物1-4和6的单一X射线结构揭示了占据香豆素环轴向位置的烷氧基,据推测是半缩醛不稳定的原因。由于轴向应变,半缩醛(1、3,5)在非酒精溶剂中加热时,很容易转化为各自的水合物(2、4和6)。这些转化的定性速率很大程度上取决于烷氧基的大小(i-Pr> Et> Me)。我们提出了一种将半缩醛转化为水合物的机制,该机制涉及色氨酸-3,4-二酮中间体,这可以通过将其捕获为二亚胺,喹喔啉杂环来证明。