Ru-Catalysed CH Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies

• Published in: Chemistry : a European journal 2015-03, Vol.21 (14), p.5380-5386
• Main Authors: Sollert, Carina, Devaraj, Karthik, Orthaber, Andreas, Gates, Paul J., Pilarski, Lukasz T.
• Format: Article
• Language: English
• Subjects: C-H activation; catalysis; CH activation; Derivatives; Functional groups; heterocycles; Indoles; Iodides; Ligands; Pyrroles; reaction mechanisms; ruthenium; Tolerances; Tryptophan
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201405931

The Ru‐catalysed C2H arylation of indoles and pyrroles by using boronic acids under oxidative conditions is reported. This reaction can be applied to tryptophan derivatives and tolerates a wide range of functional groups on both coupling partners, including bromides and iodides, which can be further derivatised selectively. New indole‐based ruthenacyclic complexes are described and investigated as possible intermediates in the reaction. Mechanistic studies suggest the on‐cycle intermediates do not possess a para‐cymene ligand and that the on‐cycle metalation occurs through an electrophilic attack by the Ru centre. High tolerance: An oxidative, Ru‐catalysed, and highly selective CH arylation of indoles and pyrroles is accomplished by using boronic acids (see picture; pym=2‐pyrimidyl). The reaction tolerates a wide range of functional groups, including aryl iodides and tryptophan derivatives. New indole‐based ruthenacycles are described and their role in the mechanism is investigated.