Disiamylborane (bis(1,2-dimethylpropyl)borane, Sia₂BH) is an

organoborane Organoborane or organoboron compounds are chemical compounds of boron and carbon that are organic derivatives of BH3, for example trialkyl boranes. Organoboron chemistry or organoborane chemistry is the chemistry of these compounds. Organoboron ...

used in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

. It is used for

hydroboration–oxidation reaction Hydroboration–oxidation reaction is a two-step hydration reaction that converts an alkene into an Alcohol (chemistry), alcohol. The process results in the Syn and anti addition, syn addition of a hydrogen and a hydroxyl group where the double bond ...

s of terminal

alkyne \ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and no ...

s, giving

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

s via anti-Markovnikov hydration followed by

tautomer Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hyd ...

ization. Disiamylborane is relatively selective for terminal alkynes and alkenes vs internal alkynes and alkenes.{{OrgSynth, author=Eric J. Leopold , title=Selective Hydroboration of a 1,3,7-Triene: Homogeraniol, volume= 64, year=1986, page=164, doi=10.15227/orgsyn.064.0164 Disiamylborane is prepared by

hydroboration In organic chemistry, hydroboration refers to the addition of a hydrogen- boron bond to certain double and triple bonds involving carbon (, , , and ). This chemical reaction is useful in the organic synthesis of organic compounds. Hydroboration ...

trimethylethylene 2-Methyl-2-butene, 2m2b, 2-methylbut-2-ene, also beta-isoamylene is an alkene hydrocarbon with the molecular formula C5H10. Used as a free radical scavenger in trichloromethane (chloroform) and dichloromethane (methylene chloride). John Snow, t ...

with

diborane Diborane(6), generally known as diborane, is the chemical compound with the formula B2H6. It is a toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Diborane is a key boron compound with a variety of applications. It has attracte ...

. The reaction stops at the secondary borane due to steric hindrance.

Related reagents

* 9-Borabicyclo .3.1onane (9-BBN). *

Thexylborane Thexylborane is a borane with the formula e2CHCMe2BH2sub>2 (Me = methyl). The name derives from "''t''-hexylborane" (although the group is not the standard ''tert''-hexyl group), and the formula is often abbreviated ThxBH2. A colorless liquid, ...

((1,1,2-trimethylpropyl)borane, ThxBH₂), a primary borane obtained by hydroboration of

tetramethylethylene Tetramethylethylene is a hydrocarbon with the formula Me2C=CMe2 (Me = methyl). A colorless liquid, it is the simplest tetrasubstituted alkene. Synthesis and reactions It is prepared by base-catalyzed isomerization of 2,3-dimethyl-1-butene. Tet ...

Naming

The name ''siamyl'' is an abbreviation for "''sec-''isoamyl".

References

Alkylboranes Reagents for organic chemistry