Electrocyclic Ring‐Opening of 1,2,4‐Oxadiazole[4,5‐a]piridinium Chloride: a New Route to 1,2,4‐Oxadiazole Dienamino Compounds

• Published in: ChemistryOpen (Weinheim) Vol. 8; no. 9; pp. 1209 - 1221
• Main Authors: Carella, Stefano, Memeo, Misal Giuseppe, Quadrelli, Paolo
• Format: Journal Article
• Language: English
• Published: Germany John Wiley & Sons, Inc 01.09.2019; John Wiley and Sons Inc; Wiley-VCH
• Subjects: 1,3-dipolar cycloadditions; Amines; Ammonia; Bicarbonates; Chlorides; Chromatography; Derivatives; dienamino derivatives; Laboratories; nitrile oxides; NMR; Nuclear magnetic resonance; Nucleophiles; Oxadiazoles; Ring opening; Zincke salts; oxadiazoles; dienamino derivatives; nitrile oxides; Zincke salts; 1,3-dipolar cycloadditions
• ISSN: 2191-1363; 2191-1363
• DOI: 10.1002/open.201900230

1,2,4‐Oxadiazole[4,5‐a]piridinium chloride adds nucleophiles to undergo electrocyclic ring opening affording 1,2,4‐oxadiazole dienamino derivatives. These pyridinium salts represent a special class of Zincke salts that are prone to rearrange when treated with primary amines or in the presence of bicarbonate to give the pyridones. The pivotal tuning of the experimental conditions leads to a straightforward synthesis of valuable 1,2,4‐oxadiazole dienamine derivatives. The mechanism is also discussed in the light of NMR experiments and theoretical calculations. Easy dienamines! 1,2,4‐Oxadiazole[4,5‐a]piridinium chloride undergoes nucleophilic addition of amines to afford 1,2,4‐oxadiazole dienamine derivatives. These pyridinium salts represent a special class of Zincke salts that are prone to rearrange when treated with primary amines or in the presence of bicarbonate to give the pyridones.