A Versatile Synthesis of Unsymmetrical 3,3′-Bioxindoles: Stereoselective Mukaiyama Aldol Reactions of 2-Siloxyindoles with Isatins

A new synthesis of 3,3′-bioxindoles is reported that is well suited for the preparation of unsymmetrical structures. In the key step, 3-hydroxy-3,3′-bioxindoles are constructed by Mukaiyama aldol reaction of 2-siloxyindoles with isatins. These tertiary carbinols are formed in high diastereoselectivities, with substitution at various positions of the isatin and the 2-siloxyindole being tolerated.

本文报道了一种适用于非对称结构制备的3,3'-双吲哚酮（3,3′-bioxindoles）全新合成方法。核心合成步骤中，通过2-硅氧基吲哚（2-siloxyindoles）与靛红（isatins）的Mukaiyama羟醛缩合反应，构建得到3-羟基-3,3'-双吲哚酮。该类3-羟基-3,3'-双吲哚酮产物可获得优异的非对映选择性，且靛红与2-硅氧基吲哚的不同位点取代基均具有良好的兼容性。