Abstract 2-Oxotryptamine and its homo derivative undergo intramolecular Mannich-type cyclization with acetone and other ketones to give spiro [indole-3, 3'-pyrrolidin]-2-ones and spiro [indole-3, 3'-piperidin]-2-ones. A similar reaction with the bis-homologue of 2- oxotryptamine to yield spiro [azepane-3, 3'-indol]-2'-ones was unsuccessful.
