Rhodium-catalyzed formation of boron–nitrogen bonds: a mild route to cyclic aminoboranes and borazines

Abstract

Secondary amine–borane adducts R₂NH·BH₃, which are stable to H₂ elimination below 100 °C, undergo efficient catalytic dehydrocoupling at 25–45 °C in the presence of Rh^I or Rh^III complexes to quantitatively form cyclic aminoboranes [NR₂–BH₂]₂ (1: R = Me or 2: cyclo-C₄H₈); under similarly mild conditions, the analogous adducts NH₃·BH₃ and MeNH₂·BH₃ yield borazines [RN–BH]₃ (3: R = H or 4: R = Me) in yields limited by intermolecular coupling reactions.