Does 9-BBN not act on internal alkynes or alkenes?

In summary, 9-BBN is a chemical compound commonly used as a reducing agent in organic chemistry reactions. It works by forming a complex with the alkene or alkyne functional group, allowing for a hydride ion to be transferred to the substrate for reduction. However, it cannot act on internal alkynes or alkenes due to steric hindrance. Other reagents such as DIBAL-H and LiAlH4 can be used for reduction on internal alkynes and alkenes. 9-BBN can also be used on other functional groups, but may require different reaction conditions and may not be as effective as other reducing agents for these groups.
  • #1
fangrz
38
0
Organic Chemistry question! Is 9-BBN too sterically hindered to even react with internal alkynes or alkenes? (to do hydroboration)
 
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  • #2
I've seen claims that 9-BBN can react with internal alkenes, but I haven't attempted it myself. I imagine the reaction would take longer than a reaction with a terminal alkene. The goal of the big substituents is to favor boron addition at less sterically hindered sites with high regioselectivity. 9-BBN generally tends to be more regioselective than something like borane-THF. You can also get it in solid form, which is easier to use than gaseous B2H6.
 
  • #3
Thanks!
 

Related to Does 9-BBN not act on internal alkynes or alkenes?

What is 9-BBN?

9-BBN (9-Borabicyclo[3.3.1]nonane) is a chemical compound that is commonly used as a reducing agent in organic chemistry reactions.

How does 9-BBN work?

9-BBN works by forming a complex with the alkene or alkyne functional group, which then allows for a hydride ion to be transferred to the substrate, resulting in reduction.

Why doesn't 9-BBN act on internal alkynes or alkenes?

This is because the steric hindrance of the internal alkyne or alkene prevents the formation of a stable complex with 9-BBN, making it difficult for the hydride ion to reach the substrate and carry out reduction.

Are there any other reagents that can be used on internal alkynes or alkenes?

Yes, there are other reducing agents such as DIBAL-H (diisobutylaluminum hydride) and LiAlH4 (lithium aluminum hydride) that can be used on internal alkynes and alkenes to achieve reduction.

Can 9-BBN be used on other functional groups?

Yes, 9-BBN can also be used on other functional groups such as ketones, esters, and nitriles to achieve reduction. However, it may require different reaction conditions and may not be as effective as other reducing agents for these functional groups.

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