Copper-CatalyzedN-Arylation of Tautomerizable Heterocycles with Boronic Acids and Its Application to Synthesis of Oxygenated Carbazoles

Abstract

A general and mild strategy has been developed for the selective N‐arylation of tautomerizable heterocycles with a series of arylboronic acids, using CuOTf as the catalyst and 1,10‐Phen as the ligand, under base free conditions at ambient atmosphere. The reaction mechanism explored by using density functional methods revealed that both kinetic and thermodynamic controls favour N‐arylation. This “open‐flask” chemistry successfully applied for N‐arylation of benzo[d] oxazol‐2(3H)‐one and the designed N‐arylated product was subsequently manipulated in synthesizing various naturally occurring oxygenated carbazole alkaloids (e. g. clausenine, clauraila A, clausenal).