Redox-neutral access to isoquinolines via cobalt(III)-catalyzed C H acylmethylation/cyclization of benzimidates with sulfoxonium ylides

A practical and highly efficient method for the regioselective synthesis of isoquinolines was developed via cobalt-catalyzed C(sp²)−H activation and subsequent intramolecular tandem annulations between benzimidates and sulfoxonium ylides. Key to the success of this transformation was the use of an inexpensive and bench-stable Cp*Co(III)-catalyst. Various functionalized isoquinolines were prepared successfully under base-free and oxidant-free conditions. This protocol features simple operation, broad substrate scope, and good functional group tolerance. Moreover, the reaction is scalable and tolerant of ambient air and moisture.