9-Borabicyclo[3.3.1]nonane
RELATED: BH3, (Sia)2BH
Most Common Use
- hydroboration of alkenes and alkynes in hydroboration-oxidations
- most common solvent is THF (tetrahydrofuran)
Hydroboration of alkynes
FGT: alkyne ➛ alkenylborane
TYPE: reduction
REGIOCHEM: anti-Markovnikov
STEREOCHEM: syn addition
9-BBN adds to alkenes and alkynes in an anti-Markovnikov fashion. It is a syn addition with the hydrogen and the borane adding to the same side of the alkene or alkyne.
Because alkynes have two pi bonds, boranes can add to them twice. 9-BBN inhibits the addition of a second borane due to its steric bulk. The steric bulk also enhances the anti-Markovnikov regioselectivity.
Like most boranes, 9-BBN exists as a dimer (shown below), which readily cleaves to the monomer (shown above) in the presence of alkenes and alkynes
