I know that mCPBA is used for epoxidation of alkenes.
But in my textbook this reaction is given :
2-methyl cyclohex-1-one + mCPBA
![right arrow :rarrow:](https://www.chemicalforums.com/Smileys/classic/rarrow.png)
β-methyl-δ-valerolactone
(a cyclic ester with carbonyl adjacent to oxygen and a methyl at the next carbon)
My observation: There is one carbon less than reactant. I think the ring contracts first... Something like favorsky rearrangement.