摘要：

The unprecedented triarylcarbonium ion-pair-catalyzed Pictet–Spengler reaction of tryptamines with aromatic aldehydes and cyclic ketones in water was disclosed. Under metal-free conditions, diverse tetrahydro-β-carbolines and spirocyclic tetrahydro-β-carbolines were obtained in good yields with excellent functional group tolerance, including late-stage modification of natural products and small molecular drugs. The practicability of this protocol is also characterized in the gram-scale synthesis of Komavine and several other functional compounds. Preliminary mechanistic studies indicated that in aqueous media the in situ -generated superacidic species from the carbonium ion pair with water was crucial to promote the Pictet–Spengler reaction.

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