Selective C3-Allylation and Formal [3+2]-Annulation of Spiro-Aziridine Oxindoles: Synthesis of 5′-Substituted Spiro[pyrrolidine-3,3′-oxindoles] and Coerulescine
Selective C3-Allylation and Formal [3+2]-Annulation of Spiro-Aziridine Oxindoles: Synthesis of 5′-Substituted Spiro[pyrrolidine-3,3′-oxindoles] and Coerulescine
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DOI：
10.1021/acs.joc.2c00863
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发表时间：
2022-06-22
影响因子：
3.6
通讯作者：
Hajra, Saumen
中科院分区：
文献类型：
--
作者：
Saleh, S. K. Abu;Hazra, Atanu;Hajra, Saumen
已证明，布朗斯台德酸和/或刘易斯酸催化的选择性C3-烯丙基化和螺氮丙啶羟吲哚与烯丙基硅烷的形式[3 + 2]环化可分别直接获得3-烯丙基-3-氨甲基羟吲哚和5-甲硅烷基甲基螺[吡咯烷-3，3 '-羟吲哚]。当使用手性螺氮丙啶时，酸催化方法不提供任何立体选择性。而非外消旋的螺氮丙啶与烯丙基格氏试剂在无催化剂条件下反应，则得到了具有良好立体选择性的3-烯丙基-3-氨甲基羟吲哚类化合物（ee高达80%）。烯丙基化方案被用于蓝花碱和各种5 '-取代的螺[吡咯烷-3，3'-羟吲哚]的短合成。
Bronsted acid-and/or Lewis acid-catalyzed selective C3-allylation and formal [3 + 2]-annulation of spiro-aziridine oxindoles with allylsilanes have been demonstrated to deliver direct access to 3-allyl-3-aminomethyl oxindoles and 5-silyl methyl spiro[pyrrolidine-3,3 '-oxindoles], respectively. The acid-catalyzed methods do not provide any stereoselectivity when chiral spiroaziridines are used. However, the reaction of nonracemic sprioaziridines with allyl-Grignard reagent under catalyst-free conditions afforded 3-allyl-3-aminomethyl oxindoles with good stereoselectivity (ee up to 80%). The allylation protocol is utilized for the short synthesis of coerulescine and various 5 '-substituted spiro[pyrrolidine-3,3 '-oxindoles].