Mn-Catalyzed Dehydrocyanative Transannulation of Heteroarenes via C-H Activation: Beyond the Permanent Directing Effects of Pyridines/Pyrimidines

Pyridine/pyrimidine rings are common and effective directing groups for catalytic activation of C-H bonds. However, they are poorly functionalizable either under in situ or ex situ conditions. Reported in this work is Mn-catalyzed dehydrocyanative transannulation between three classes of heteroarenes and propargyl carbonates. The pyridyl/pyrimidyl groups in the heteroarenes initially function as a directing group to enable C-H allenylation; they then undergo intramolecular Diels-Alder-retro Diels-Alder reactions with the allene moiety to afford fused carbo/heterocycles. Three key intermediates at different stages of the reaction have been isolated.