Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032 (India).
Angew Chem Int Ed Engl. 2015 Dec 21;54(52):15831-5. doi: 10.1002/anie.201508746. Epub 2015 Nov 19.
Aprocess for the assembly of carbazole alkaloids has been developed on the basis of ring-closing metathesis (RCM) and ringrearrangement-aromatization (RRA) as the key steps. This method is based on allyl Grignard addition to isatin derivatives to provide smooth access to 2,2-diallyl 3-oxindole derivatives through a 1,2-allyl shift. The diallyl derivatives were used as RCM precursors to afford a novel class of spirocyclopentene-3-oxindole derivatives, which underwent a novel RRA reaction to afford carbazole derivatives. The synthetic sequence to carbazoles was shortened by combining the RCM and RRA steps in an orthogonal tandem catalytic process. The utility of this methodology was further demonstrated by the straightforward synthesis of carbazole alkaloids, including amukonal derivative, girinimbilol, heptaphylline, and bis(2-hydroxy-3-methylcarbazole).
已开发出一种基于环 closing metathesis (RCM) 和 ringrearrangement-aromatization (RRA) 的咔唑生物碱的组装方法，作为关键步骤。该方法基于烯丙基 Grignard 添加到靛红衍生物，以通过 1,2-烯丙基移位顺利提供 2,2-二烯丙基 3-氧吲哚衍生物。二烯丙基衍生物用作 RCM 前体，以提供新型的螺环戊烯-3-氧吲哚衍生物，其经历新颖的 RRA 反应以提供咔唑衍生物。通过在正交串联催化过程中组合 RCM 和 RRA 步骤，咔唑的合成序列缩短。该方法的实用性通过咔唑生物碱的直接合成进一步得到证明，包括 amukonal 衍生物、girinimbilol、heptaphylline 和双(2-羟基-3-甲基咔唑)。
