Intramolecular Heterocyclization of O-Propargylated Aromatic Hydroxyaldehydes as an Expedient Route to Substituted Chromenopyridines under Metal-Free Conditions

A concise and regioselective approach to the synthesis of chromenopyridine and chromenopyridinone derivatives was developed. The synthetic strategy relies on the O-propargylation of aromatic hydroxyaldehydes followed by reaction with propargylamine. The intramolecular cycloaddition reaction between the alkyne and azadiene, which is formed as an intermediate, furnished the desired skeletons.