tert-Butyl 5-cyano-1H-indole-1-carboxylate is used as a key intermediate in the synthesis of pharmaceutical compounds, particularly in the development of indole-based drugs. The cyano group at the 5-position and the tert-butoxycarbonyl (Boc) protecting group on the indole nitrogen allow for selective chemical modifications. The Boc group temporarily protects the nitrogen, which can be deprotected later to enable further reactions, while the cyano functionality can be transformed into carboxylic acids, amides, or other groups, making it valuable in medicinal chemistry for constructing complex heterocyclic systems. It is commonly employed in the preparation of serotonin receptor modulators and other bioactive molecules targeting neurological and psychiatric disorders, as well as in broader applications like anti-cancer and anti-inflammatory agents. Also utilized in research settings for generating analogs in structure-activity relationship (SAR) studies.