Diruthenium(II,II) tetrakis(acetate) as a catalyst of choice for intermolecular insertion of stabilized diazocompounds into OH bonds

In the presence of 3 mol% of [Ru(OAc)2]2 at 90°C in hexafluorobenzene or alcohols as solvents the highly stabilized diazocoumarin 1 undergoes insertion into the OH bond of alcohols (and phenols) regio- and chemoselectively, affording the corresponding 3-alkoxy-4-hydroxycoumarin in moderate to excellent yields.