We report an efficient method for the direct β-acylation of 2-ylideneoxindoles with acyl chlorides that is catalyzed by organophosphanes in the presence of base. A variety of functionalized 2-ylideneoxindoles were prepared in moderate to good yields under mild, metal-free conditions via a tandem phospha-Michael/O-acylation/intramolecular cyclization/rearrangement sequence. Mechanistic investigations revealed that C–O bond cleavage on a possible betaine intermediate is the key step for the installation of the keto-functionality at the β-position of 2-ylideneoxindoles in a highly stereospecific manner. The synthetic utility of this protocol could also be proven by a scale-up reaction and synthetic transformations of the products.

中文翻译：

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有机磷烷催化通过直接 β-酰化构建功能化 2-Ylideneoxindoles

我们报告了一种在碱存在下由有机膦催化的 2-亚基羟吲哚与酰氯直接 β-酰化的有效方法。在温和、无金属的条件下，通过串联的磷酸-迈克尔/O-酰化/分子内环化/重排序列，以中等至良好的产率制备了各种功能化的 2-亚基羟吲哚。机理研究表明，在可能的甜菜碱中间体上的 C-O 键断裂是以高度立体定向的方式在 2-ylideneoxindoles 的 β 位安装酮基官能团的关键步骤。该协议的合成效用也可以通过产品的放大反应和合成转化来证明。