Nicholas reaction

The Nicholas reaction is an organic reaction where a dicobalt octacarbonyl-stabilized propargylic cation is reacted with a nucleophile. Oxidative demetallation gives the desired alkylated alkyne.



Several reviews have been published.

Reaction mechanism


The addition of dicobalt octacarbonyl to a propargylic ether (1) gives the dicobalt intermediate 2. Reaction with HBF4 or Lewis acid gives the key dicobalt octacarbonyl-stabilized propargylic cation (3a and 3b). Addition of a nucleophile followed by a mild oxidation gives the desired substituted alkyne (5).