The oxidation of aldehydes and alpha-diketones with peroxy compounds

Recently, I have been reading up on the [Baeyer-Villiger (BV) oxidation](https://en.wikipedia.org/wiki/Baeyer%E2%80%93Villiger_oxidation). The oxidation is most commonly discussed for ketones. However, the oxidation also works for aldehydes and $\alpha$-diketones (Rojas, 2015).


[![enter image description here](https://i.stack.imgur.com/pKhBP.png)](https://i.stack.imgur.com/pKhBP.png)


The above image is Scheme 2.2 from Rojas (2015). 


I have mainly two queries: 


1. Does the oxidation of aldehydes to carboxylic acids by peroxy compounds, such as peracids, proceed via a BV oxidation where the hydride is the migrating group? This would be seemingly different from the oxidation mechanism for the oxidation by $\ce {MnO4^-}$ or $\ce {CrO3}$ where the aldehyde is oxidised when it is in the gem-diol form.
2. Why does the oxidation of $\alpha$-diketones yield the corresponding anhydride and not an $\alpha$-ketoester? This is extremely puzzling because the acyl group is terribly bad at stabilising any partial positive charges on the acyl carbon. How is it possible that such a BV oxidation can occur?


**Reference**


Rojas, C. M. (2015). Molecular Rearrangements in Organic Synthesis (1st ed.). Hoboken, New Jersey: John Wiley & Sons, Inc. 




The Baeyer-Villiger oxidation is conducted under acidic conditions such as an alkyl peroxide in the presence of a mineral acid (e.g.; H2SO4) or a peracid (e.g.; peracetic acid or m-chloroperbenzoic acid). In the reactions described in the diagram, the reactions of aldehyde **1** or α-diketone **7** are initiated by proton of the carbonyl oxygen followed by addition of peroxide (an alkylperoxide is illustrated). Ultimately, the oxygen of the RO-moiety is protonated and is the effective leaving group (ROH) in the rearrangement. In both sequences, the red route is favored; the blue route disfavored. Cation **3** is a more stable species than cation **5** because of hyperconjugation with the alkyl group or resonance stabilization if R'=aryl. Cation **3** affords a carboxylic acid while cation **4** would lead to formate ester **6**.  
  

In the case of peroxyhemiketal **8**, acyl migration leads to cation **9** which is more stable than species **11,** which has a positive charge adjacent to a carbonyl group, which is destabilizing. Thus, anhydride **10** is formed in preference to α-ketoester **12**. 
  
  

[![enter image description here](https://i.stack.imgur.com/ileIo.jpg)](https://i.stack.imgur.com/ileIo.jpg)


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