Mn‐Catalyzed Dehydrocyanative Transannulation of Heteroarenes and Propargyl Carbonates through C−H Activation: Beyond the Permanent Directing Effects of Pyridines/Pyrimidines

: Pyridines/pyrimidines are common and effective directing groups in C-H activation. However, they are poorly functionalizable heteroarenes. 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 directing groups 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 were isolated.