Transition-Metal-Free Synthesis of Substituted Pyridines via Ring Expansion of 2-Allyl-2H-azirines

A new strategy to open the 2-allyl-2H-azirines by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) promotion in metal-free conditions affording 1-azatrienes that in situ electrocyclize to the pyridines in good to excellent yields is reported. 1:22 The reaction displays a broad substrate scope and good tolerance to a variety of substituents including aryl, alkyl, and heterocyclic groups. In addition, one-pot synthesis of pyridines from oximes via in situ formation of 2H-azirines was achieved.