A Lewis acid-catalyzed nucleophilic addition of electron rich aromatics with 3-hydroxy-2-oxindoles 5 was developed. The reaction is believed to proceed through the 2H-indol-2-one ring system 9, which eventually reacts with various electron-rich aromatics to afford a variety of 2-oxindoles with an all-carbon quaternary center at the pseudobenzylic position (4, 8, 13, and 16) in high yields. The methodology provides an expeditious route to the tetracyclic core (3) of diazonamide (1), and azonazine (2) as well as the tricyclic core of asperazine (6a), idiospermuline (6b), and calycosidine (6c) viz. C(3a)-arylpyrroloindolines 7 having an all-carbon quaternary center on further synthetic elaboration.
开发了一种
路易斯酸催化的富电子芳香化合物与3-羟基-2-氧
吲哚 5 的亲核加成反应。该反应被认为是通过
2H-吲哚-2-酮环系 9 进行的,最终与各种富电子芳香化合物反应,生成多种具有全碳季
铵中心的2-氧
吲哚(4、8、13和16),产率高。这一方法提供了合成二氮酰胺(1)和氮杂啶(2)的四环核心(3)以及某些
三环核心的高效途径,如asperazine(6a)、idiospermuline(6b)和calycosidine(6c),即在进一步合成扩展下具有全碳季
铵中心的C(3a)-芳基
吡咯吲哚类化合物 7。