Baeyer Villiger Rearrangement

Reaction that involves the oxidation of ketones to esters by Carbon-Carbon bond cleavage of the carbonyl group and the introduction of an oxygen atom adjacent to it when treatment with peracids such as m-chloroperoxybenzoic acid(mCPBA), peroxyacetic acid(PAA), perbenzoic acid(PBA), permono sulphuric acid, peroxytrifluoroacetic acid(TFPAA), Hydrogen peroxide/BF₃ or Sodium percarbonate (Na₂CO₃.1.5H₂O₂) etc. Cyclic ketones converted into lactones with ring expansion.

Baeyer-villiger rearrangement reaction of unsymmetrical ketones is regioselective. The substituents which can stabilize the positive charge can migrate readily. The migratory aptitude order in Baeyer villiger oxidation for various substituents is given below-
H > tert-alkyl > cyclohexyl > sec- alkyl > benzyl > aryl > primary - alkyl > methyl.
The configuration of the migrating chiral substituent is retained because it is a concerted process.