Rapid Acyl Migration between Pyrogallyl 1,2- and 1,3-Dipivaloates

Pyrogallol and its derivatives are biologically active compounds, and pyrogallol also forms the basis of an increasingly important tetrameric supramolecular scaffold. Pyrogallol[4]arenes are tetrameric macrocycles that form from 1,2,3-trihydroxybenzene and aldehydes under acidic conditions. Pyrogallol was treated with two equivalents of pivaloyl chloride to form pyrogallyl dipivaloate. A mixture of regioisomers was invariably obtained and a rapid equilibrium was observed between the 1,2- and 1,3-diesters in polar solvents. A pure sample of solid pyrogallyl 1,2-dipivaloate was isolated and its crystal structure was obtained. The pure compound was shown to rearrange to mixtures similar to those isolated initially.