Dimethyldioxirane epoxidation of benzofurans: reversible thermal and photochemical valence isomerization between benzofuran epoxides, quinone methides, and benzoxetenes
作者:Waldemar Adam、Lazaros Hadjiarapoglou、Karl Peters、Markus Sauter
DOI:10.1021/ja00072a012
日期:1993.9
Low-temperature oxidation of the four possible regioisomeric methoxy-substituted benzofurans 1 by dimethyldioxirane afforded the rather labile epoxides 2, which are in equilibrium with their equally labile quinone methides 3 through reversible valence isomerization. Photochemical cyclization of the latter afforded the hitherto unknown benzoxetenes 4, which are sufficiently persistent at subambient
四种可能的区域异构甲氧基取代的苯并呋喃 1 被二甲基二环氧乙烷低温氧化得到相当不稳定的环氧化物 2,它们通过可逆的价异构化与其同样不稳定的醌甲基化物 3 处于平衡状态。后者的光化学环化提供了迄今为止未知的苯并氧杂环丁烯 4,其在低于环境温度下具有足够的持久性以进行光谱表征。不稳定的氧杂环丁烯 4 缓慢恢复为环氧化物 2 和醌甲基化物 3 的平衡混合物,如在苯并呋喃 1 的二环氧乙烷环氧化中获得的相同