Ring Opening Reduction of Cyclic Anhydrides Catalyzed by Tris(pentafluorophenyl)Borane Using Hydrosilanes as Hydride Source

Hydrosilanes are widely used as reducing agents in reduction of carbonyl groups, and various catalysts have been developed for the activation of hydrosilanes, majority of them being transition metal-based. A main-group-based Lewis acid tris(pentafluorophenyl)borane (BCF) has gained increasing attention due to its Lewis acidity and versatility along with being non-metal. Herein we describe the BCF-catalyzed ring opening reduction of cyclic anhydrides using hydrosilanes as a source of hydrides. The reduction affords unsymmetrical bis(silyl) protected hydroxy-acids, leading to an efficient way for the synthesis of silyl ester functionalities. The capability of forming protected hydroxyacids under mild conditions with high yields in one step is also advantageous. A range of hydrosilanes and cyclic anhydrides can be employed with quantitative conversion, high yields, relatively fast reaction time and mild reaction conditions. NMR spectroscopy is used in the characterization of the products, along with insight to the potential mechanism.