Efficient Entry to Diversely Functionalized Spirocyclic Oxindoles from Isatins through Carbonyl-Addition/Cyclization Reaction Sequences
摘要:
A novel approach to diversely functionalized spirocyclic oxindoles has been developed by using different metal-mediated carbonyl-addition/cyclization reaction sequences. Spirocyclization precursors, 2-indolinonetethered homoallylic alcohols, (buta-1,3-dien-2-yl)methanols, and alpha-allenols have been obtained by regioselective addition of stabilized organoindium reagents to isatins in aqueous environment. Ruthenium-, silver-, and palladium-catalyzed reactions of the above unsaturated alcohol derivatives provided oxaspiro oxindoles.
A versatile photochemical ring-expansion protocol for the synthesis of oxacyclic spirooxindoles under catalyst-free conditions is described. The reaction is enabled by the use of unstrained O-containing heterocycles with 3-diazoindolin-2-ones under visible-light irradiation. Several synthetic advantages for this method are exhibited, including mild conditions, good functional group tolerance, operational
描述了在无催化剂条件下合成 oxacyclic spirooxindoles 的多功能光化学扩环协议。该反应是通过在可见光照射下使用未应变的含 O 杂环和 3-二氮并吲哚-2-酮来实现的。展示了该方法的几个合成优势,包括温和的条件、良好的官能团耐受性、操作简单性和可扩展性。机理研究表明,转化可能通过氧鎓叶立德中间体的形成,然后是离子环化来进行。