Acid-Catalyzed Cyclization Reactions of Substituted Acetylenic Ketones: A new Approach for the Synthesis of 3-Halofurans, Flavones, and Styrylchromones
作者:Daniel Obrecht
DOI:10.1002/hlca.19890720305
日期:1989.5.3
Acetylenic acetals of type I(Scheme 1) and acetylenic ketones of type III(Scheme 1), 37 and 38(Scheme 7) are versatile synthetic precursors for the synthesis of various heterocycles by acid-catalyzed cyclization reactions. By this way, substituted 3-halofurans of type II and IV(Scheme 1) and flavones and styrylchromones (Scheme 7) can be synthesized in good-to-excellent yields. The high degree of regioselectivity
I型乙缩醛(方案1)和III型乙炔酮(方案1),37和38 (方案7)是用于通过酸催化的环化反应合成各种杂环的通用合成前体。通过这种方式,可以以良好至优异的产率合成II和IV型取代的3-卤代呋喃(方案1)以及黄酮和苯乙烯基色酮(方案7)。3-卤代呋喃酮合成中的高度区域选择性(方案4)是HX(X = Cl,Br,I)的区域选择性β加成到乙炔醛和乙炔酮部分的结果。方案5中描述了一种可能的机制。由于3-氟呋喃很容易被金属化和取代,因此这种方法构成了高度取代的呋喃的新合成方法。