AlCl3‑Promoted Selective Michael Addition with Allenoate and Methyleneindolinone: Synthesis of Spirocyclic Oxindole by Using Allenoate as a Four-Carbon Component Building Block

The AlCl3-promoted cyclization of readily available allenoates with methyleneindolinone is disclosed. The present strategy provides a rapid access to spirocyclic oxindole-cyclohexenones in an efficient manner. Remarkably, the allenoate is implemented as a four-carbon (4C) component to form the ring, which shows high synthetic efficiency. Flexibility of this method allows quick synthesis of spirocyclic oxindole-dihydropyrans by varying one of the components. It is also noteworthy that AlCl3 serves as the chlorine source as well as an effective catalyst to facilitate this interesting transformation.本研究报道了三氯化铝（AlCl3）介导的、由易得联烯酸酯与亚甲基吲哚酮参与的环化反应。该合成策略可高效快速构建螺环氧化吲哚-环己烯酮类骨架。值得注意的是，本反应中联烯酸酯作为四碳（4C）组分参与成环，展现出极高的合成效率。通过调整反应组分，该方法还可灵活用于快速合成螺环氧化吲哚-二氢吡喃类化合物。此外，三氯化铝同时充当氯源与高效催化剂，促成了这一有趣的转化过程。