Direct Pyrido-Annulation of 2-Chloro-3-carbonyl Indoles with 1,3-Dipolar Azomethine Ylides: An Adaptable One-Flask Access to Substituted β-Carboline-1-carboxylates

An efficient, economical, indole-to-β-carboline strategy has been devised through a convenient, one pot, catalyst-free operation. The key tactic in this endeavor involves pyrido-annulation of 2-chloro-3-carbonyl indoles through regioselective (3 + 3)-annulation with 1,3-dipolar azomethine ylides to provide direct access to a range of β-carbolines in decent yields. Overall our methodology constitutes an adaptable access to a range of bioactive β-carbolines (27 examples) with complete regioselectivity and robust functional group compatibility.