The efficient synthesis of biologically active spiro compounds is a challenge for organic chemists and pharmaceutical chemists. Herein we describe a synthesis strategy of spirocyclic oxindoles via double Michael reaction of N-protected-oxindoles to dienones using tetrabutylammonium bromide (TBAB) as catalyst. The desired spirocyclic oxindoles were obtained with both high yields up to 99% and diastereoselectivity up to >95:5 dr.

中文翻译：

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TBAB催化的二烯类化合物中双吲哚的双迈克尔加成反应：一种高效的制备螺环式氧化吲哚的途径

生物活性螺化合物的有效合成是有机化学家和药物化学家的挑战。在本文中，我们描述了通过使用四丁基溴化铵（TBAB）作为催化剂的N-保护的羟吲哚与二烯酮的双迈克尔反应，合成螺环羟吲哚的合成策略。以高达99％的高收率和高达> 95：5 dr的非对映选择性获得了所需的螺环羟吲哚。