# Osmium tetroxide and meta-chloroperoxybenzoic acid

Can these be used to induce acetal ring closures? For example, when dealing with a molecule that has both a C=O functional group and an alkene as part of its structure and there is the possibility of creating a 5 or 6 membered ring through intramolecular -OH attack on the C=O ... can we just use the $\ce{OsO4}$ to create the diol and expect it to provide us sufficient acidity to catalyze ring closure?

Same question goes for meta-chloroperoxybenzoic acid.

• It's not unusual for hydroxy-esters to cyclize and form a lactone especially if a 5- or 6-membered ring can be formed. With a diol (from osmium tetroxide) you might get a thermodynamically controlled mixture of products. M-chloroperoxybenzoic will produce an epoxide. Acid catalyzed opening of the epoxide could yield stereoisomers which could also lead to a mixture of possible lactones. – ron Oct 28 '14 at 21:58
• @ron but will the osmium tetroxide be acidic enough to form an lactone? – Dissenter Oct 28 '14 at 22:06
• Just a guess, but I would think so. If the lactone is thermodynamically more stable than the hydroxyl-ester, then closure should occur under neutral conditions. – ron Oct 28 '14 at 22:16