Ru(II)-Catalyzed β‑Carboline Directed C–H Arylation and Isolation of Its Cycloruthenated Intermediates

A Ru­(II)-catalyzed C–H arylation approach has been developed utilizing β-carboline alkaloids as the directing group. Selective formations of diarylated products from moderate to excellent yields were accomplished. Broad substrate scope with excellent functional group tolerance for C1-phenyl/thienyl/PAHs-β-carbolines was demonstrated. X-ray crystal structure of cycloruthenated complex 2cr and no arylation reaction with model substrate 13 strongly suggests that N2 is the directing group than N9 in C1-aryl-β-carbolines. Catalytic properties and stability of the cycloruthenated complexes have been explored. Library of biologically relevant new β-carboline derivatives and isolation of its cycloruthenated intermediates are the highlights of this work.