Mechanism of hydrolysis of polycyclic oxetan

The reaction is this: ![](https://i.gyazo.com/6d226e59cd826dd033fb62fe712dd265.png)


The only idea I have thus far is if we have a chloride acid that can form an ester, then we might be able to find a suitable mechanism. This would require a chloride reagent. 




I have drawn a mechanism but I haven't checked for any references as I am at home now, so it's more like paper chemistry. The chlorine atoms should play some role and possibly disfavour formation of certain carbocations that you would expect in a standard Wagner - Meerwein. It is possible to draw a concerted mechanism (not shown here) but seems very unlikely


\*\*EDIT: I have changed my initial mechanism so it explains better the methyl ester formation (see the comments below). The stereochemistry at C\* has also been corrected.


As a general comment you cannot propose a non trivial mechanism without drawing one, it is handwaving. So I did.


![Mech2](https://i.stack.imgur.com/kPczu.jpg)


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I haven't looked at the literature either, but it seems to go like this:


* protonation at the oxetane
* ring-opening of the oxetane. This gives a tertiary carbenium ion and the keto group (elimination of HCl from the $\alpha$-chloroalcohol).
* skeletal rearrangement to yield the dioxocarbenium ion; the resonance stabilization is what provides the driving force
* nucleophilic attack of solvent, to lose a methyl group and form the methyl ester


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