Acceptorless Dehydrogenation of Alcohols to Carboxylic Acids Catalyzed by Nickel (II) Complexes Under Air

ABSTRACT Here, we have synthesized two air stable, phosphine‐free nickel–Schiff base complexes, 1a , [Ni(L 1 ) 2 ](ClO 4 ) 2 (L 1 = N ‐phenyl‐1‐(pyridin‐2‐yl)methanimine) and 1b , [Ni(L 2 ) 2 ](ClO 4 ) 2 (L 2 = 1‐(6‐bromopyridin‐2‐yl)‐ N ‐(4‐methoxyphenyl)methanimine), and used them efficiently to catalyze the acceptorless dehydrogenation reaction of primary alcohols to carboxylic acids under aerobic conditions at 100°C. This methodology offers an atom‐economical and sustainable approach for preparing various carboxylic acid derivatives by employing alcohols with KOH in the presence of the catalyst. The protocol was scrutinized across a range of aliphatic and aromatic alcohols, providing corresponding carboxylic acids with moderate to excellent yield. Additionally, mechanistic insights of the reaction were also investigated through intermediate mass analysis and controlled experiments.