Hydroborane Cleavage

The defunctionalization of per-oxygenated compounds has great potential to transform readily available carbohydrate biomass into stereochemically defined materials that are difficult to access otherwise. Drawing inspiration from their previous studies, the simple switch from a hydrosilane to a hydroborane has produced novel reactivity using the same sugar precursors and was recently published in ACS Catalysis by Jared Lowe, Youngran Seo and Michel Gagne. Changing the size of the protecting group can also impact selectivity. The reaction proceeds at room temperature under mild conditions.

Using density functional theory to begin unraveling the mechanism of reduction has revealed that the borane reductant prefers to adopt a four-coordinate boronium ion (B(OR)4+), suggesting that other oxygen atoms present in the substrate can help direct the observed reactivity. This is the key difference between the hydroborane and hydrosilane reductant, which the Gagne Group will continue to be exploited in future studies.