Uncover the strength of polyhedral dicarbaboranes as the next generation of superbases in organocatalysis
- Jan Vrána
- Zuzana Kapustová
- Martin Kamlar
- Peter Šramel
- Petr Vosáhlo
- Zdeňka Růžičková
- Josef Holub
- Jan Veselý
- Aleš Růžička
2026-08-26
Although boron compounds appear in many chemical transformations, it is hard to imagine, these usually Lewis acidic, species would act as Lewis bases or even base-catalysts. Here we show that the adduct o- 2 , formed by the reaction of closo −1,2-dicarbadecaborane(10) with two equivalents of an N -heterocyclic carbene, exhibits superbasic properties with proton affinity surpassing that of the parent carbene as well as commercial superbases. It reacts selectively with C-acids, solvents and water, with its reactivity strongly influenced by substrate pK A . o- 2 facilitates various Lewis base-catalyzed transformations—including aldol condensation, the Thorpe reaction, Michael addition, Robinson annulation and β-nitrostyrene polymerization—with exceptional efficiency and selectivity. Moreover, o- 2 effectively catalyzes highly diastereoselective conjugate additions of 4-substituted pyrazolones to electron-poor olefins and spirocyclizations of pyrazolones with dibenzylideneacetones. A notable tolerance of catalyst to significant amounts of water and base-sensitive functional groups has also been observed.