Description: Treatment of an aldehyde or ketone with a peroxyacid (RCO3H) results in the formation of an ester.
Notes: A common peroxyacid for this purpose is m-chloroperoxybenzoic acid (m-CPBA), although other peroxyacids such as peroxyacetic acid can be used.
Notes: The reagent in the second example is mCPBA, drawn out. Note that in the second example, the phenyl group “migrates” preferentially over the methyl group. The reason is often not explored deeply in introductory courses, but has to do with the superior ability of the phenyl group to stabilize positive charge in the transition state (relative to methyl). For more information on “migratory aptitudes” see this link.
Mechanism: This is shown with a generic R for the peroxyacid, since a variety of different reagents can be used. Addition (“1,2-addition”) of the peroxyacid oxygen to the ketone (Step 1, arrows A and B) to give a tetrahedral intermediate is followed by a proton transfer (Step 2, arrows C and D). Then, as the C-O π bond reforms, a 1,2-shift of carbon to oxygen occurs, breaking the C–C bond as well as the weak O–O bond, giving an ester (Step 3, arrows E, F and G). Then, deprotonation yields the neutral ketone (Step 4, arrows H and I)
Notes: The neutral carboxylic acid is a byproduct here. The group “B” for deprotonation could be any atom with a lone pair, such as another equivalent of the carboxylic acid. Finally, it is plausible to show protonation of the carbonyl oxygen first (this would result in a more reactive carbonyl carbon).
(Advanced) References And Further Reading
- Einwirkung des Caro’schen Reagens auf Ketone
Adolf von Baeyer, Victor Villiger
Ber. 1899, 32 (3), 3625
This paper by Nobel Laureate Adolf von Baeyer first describes what is now known as the Baeyer-Villiger rearrangement, using a mixture of sodium persulfate and concentrated sulfuric acid (Caro’s acid).
- Cycloadditions. 23. Synthetic approaches to .alpha.-methylene-.gamma.-lactones via cycloadditions of ketenes
Alfred Hassner, Harold W. Pinnick, and Jay M. Ansell
The Journal of Organic Chemistry 1978 43 (9), 1774-1776
This paper has a representative procedure for a Baeyer-Villiger oxidation in the experimental section.
- 100 Years of Baeyer–Villiger Oxidations
Michael Renz and Bernard Meunier
Eur J. Org. Chem. 1999, 4, 737
This review on the Baeyer-Villiger oxidation includes a detailed historical perspective on the development and history of the reaction.
- The Baeyer–Villiger Oxidation of Ketones and Aldehydes
Krow, G. R. React. 1993, 251
This long, detailed review includes an in-depth discussion of the mechanism, substrate scope, limitations, and experimental procedures for the Baeyer-Villiger oxidation.
- The Baeyer−Villiger Reaction: New Developments toward Greener Procedures
E-J. ten Brink,I. W. C. E. Arends, and, and R. A. Sheldon
Chemical Reviews 2004 104 (9), 4105-4124
This review gives a modern perspective on the Baeyer-Villiger oxidation and describes procedures using more environmentally friendly oxidants (e.g. O2).