Preparation and Properties of (Hydroxymethyl)boronic Acid and its Pinanediol Ester

Hydrolysis of diisopropyl (bromomethyl)boronate followed by reaction with pinanediol provides an efficient route to pinanediol (hydroxymethyl)boronate (12), a useful intermediate for asymmetric synthesis. The stability of (hydroxymethyl)boronic acid (10) and its ester 12 have been examined by NMR spectroscopy. Heating for 1 h in acidic D2O does not degrade 10 and only affects the pinanediol moiety of 12. Base does not degrade 10 or 12 in several days at 20–25°C, but converts either to DCH2OD and CH3OD in a few h at 90–98°C, with a large H/D isotope effect. Pinanediol (bromomethyl)boronate with sodium hydroxide in D2O yields a gross mixture of products.