Metal‐Free Construction of Benzazepinoindoles in Water Enabled by an Ion‐Pair Superacidic Precatalyst

ABSTRACT Benzazepinoindole architectures have gained increasing prominence in contemporary synthetic and medicinal chemistry owing to their structural complexity and biological relevance. However, efficient and selective approaches to benzazepinoindole frameworks remain limited and often require harsh conditions or multistep sequences. In this study, we describe an ion‐pair‐catalyzed strategy for the synthesis of benzazepinoindole derivatives that circumvents the limitations of traditional Brønsted acid activation. The protocol proceeds through an indole C3‐alkylation followed by a Ph 3 C + [B(C 6 F 5 ) 4 ] − catalyzed Pictet–Spengler cyclization using α ‐keto esters and isatin, enabling enhanced electrophilic activation, and improved control over reactivity under mild conditions. Notably, all products feature a quaternary stereogenic carbon center. This method provides efficient access to structurally complex benzazepinoindole frameworks.