How do dihydroxylation addition reactions work?

Question

How do dihydroxylation addition reactions work? What are the mechanisms behind them?

I have a few questions featuring these but my textbook only went through them briefly. How do they work for H30 and for OsO4?

Answer 1

Dihydroxylation with OsO4 proceeds via cycloaddition with an alkene to form what is called an osmate ester. The osmate ester is then attacked at osmium by water (hydrolysis), ultimately leading to formation of the diol product. The most common application of this type of dihydroxylation is in the form of the Upjohn Reaction, in which OsO4 is only used in catalytic quantities and is turned over by a stoichiometric amount of external oxidant. You can read more about this here: Upjohn Dihydroxylation