The diboranes(4) bis(catecholato)diborane (B2Cat2) and bis(pinacolato)diborane (B2Pin2) are important precursors for
organoboronic esters, which are versatile reagents for the formation of C–C bonds.
Holger Braunschweig and Frank Guethlein, Julius-Maximilians-Universität Würzburg, Germany, report a new one-step procedure for the synthesis of B2Cat2 and B2Pin2, by metal-mediated, catalytic dehydrocoupling of the commercially available boranes HBCat and HBPin.
Although the homocoupling of both boranes using both homogeneous and heterogeneous catalysts was successful, the practice of continuous removal of B2Cat2 and B2Pin2 provided a marked increase in efficiency. This effect was particularly salient in the synthesis of B2Cat2 with platinum on alumina, which proceeded with turnover numbers of up to 11 600. Further studies, including the use of different catalysts and boranes, are ongoing.
- Transition-Metal-Catalyzed Synthesis of Diboranes(4),
Holger Braunschweig, Frank Guethlein,
Angew. Chem. Int. Ed. 2011.