Illustrated Glossary of Organic Chemistry

9-BBN: IUPAC name 9-borabicyclo[3.3.1]nonane. When used in the hydroboration-oxidation reaction, this sterically-hindered organoborane strongly favors formation of the less highly substituted alcohol product.

9-BBN dimer
9-BBN is synthesized by the hydroboration of 1,5-cyclooctadiene with borane-methyl sulfide complex.


A primary alcohol
Major product

A secondary alcohol
Minor product
When 9-BBN is used for the hydroboration-oxidation of styrene, 2-phenylethanol is the major product. This is an example of a regioselective reaction.