Wibaut‐Arens Alkylation

The preparation of 4‐ethylpyridine by reductive alkylation of pyridine with acetic anhydride and zinc dust is known as the Wibaut–Arens alkylation or Wibau–Arens reaction. All the mechanistic features of this reaction have been discussed. It has been reported that intermediate decomposes to give equal amount of pyridine and 4‐acetylpyridine, and the latter is then reduced to 4‐ethylpyridine by zinc. Due to the steric hindrance for the potential dimerization of 2‐position radical, 2‐ethylpyridine has never been obtained from this reaction. This reaction has been modified by the treatment of pyridine with acid anhydride and iron instead of zinc. This reaction is useful in the preparation of pyridine derivatives, especially for the isonicotinic acid derivatives.