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

Secondary amine-borane adducts R2NH . BH3, which are stable to H-2 eliminat ion below 100 degreesC, undergo efficient catalytic dehydrocoupling at 25-4 5 degreesC in the presence of Rh-I or Rh-III complexes to quantitatively fo rm cyclic aminoboranes [NR2-BH2](2) (1: R = Me or 2: cyclo-C4H8); under sim ilarly 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 intermol ecular coupling reactions.