Optimization of pinacol coupling in aqueous media

Abstract

The optimization of magnesium as well as Al–KOH mediated pinacol coupling of benzaldehyde is described. Exchange of the magnesium turnings for magnesium powder permitted the use of a significantly lower excess of magnesium and shortened the reaction time, while the conversion of starting material as well as the yields of products were preserved. Ultrasound had a beneficial effect on the reaction using magnesium. Using water instead of methanol as the reaction medium for Al–KOH mediated reactions resulted in raising the yields. The lowering of the Al∶KOH ratio was also possible.