The Favorskii reaction is the nucleophilic attack of a terminal alkyne with acidic protons on a carbonyl group. The reaction was discovered in the early 1900s by the Russian chemist Alexei Yevgrafovich Favorskii.
Contents
When catalyzed by acid, this reaction is called the Meyer–Schuster rearrangement.
Reaction mechanism
A metal acetylide is formed in situ when an alkyne is treated with a strong bases such as a hydroxide or an alkoxide. The metal acetylide then reacts with an aldehyde or ketone to form a propargyl alcohol. When an α-hydrogen is present (as is the case when the carbonyl is an aldehyde), it will tautomerize to the corresponding enone.
Protecting group
This reaction is used to protect alkynes: the alkyne is either converted with acetone to a 2-hydroxyprop-2-yl-alkyne or a protected alkyne can be directly synthesized using the commercially available 2-methyl-3-butyn-2-ol as an the alkyne source. The protective group can be removed by heating the compound in a solution of potassium hydroxide in propan-2-ol (a retro-Favorskii reaction).