Electrostatic Catalyst Generated from Diazadiborinine for Carbonyl Reduction

Since the seminal discovery by van der Waals in the late 19^th century that weak attractive forces exist between even electrically neutral atoms or molecules, a number of noncovalent interactions have been recognized. Among them, electrostatic interactions such as hydrogen bonds play pivotal roles in countless chemical processes and biochemical living systems. By mimicking biocatalysis, various organocatalysts equipped with hydrogen-bond functionality have been developed; however, a challenge has persisted in designing catalysts exploiting other types of noncovalent interactions. Here, we report metal-free hydroboration reactions of carbonyl compounds and CO₂ catalyzed by aromatic diazadiborinine. A joint experimental and computational study on the reaction mechanism suggests that adducts of diazadiborinine with carbonyl and CO₂ formed at the initial stage of the reactions serve as actual catalysts. The former stabilizes the transition state by using the electrostatic interaction between the hydride of borane and the polar, hole-shaped structure of the adduct.