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

organoborane Organoboron chemistry or organoborane chemistry studies organoboron compounds, also called organoboranes. These chemical compounds combine boron and carbon; typically, they are organic derivatives of borane (BH3), as in the trialkyl boranes. Or ...

with the formula (abbreviation: Sia₂BH). It is a colorless waxy solid that is used in

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

for

hydroboration–oxidation reaction Hydroboration–oxidation reaction is a two-step hydration reaction that converts an alkene into an alcohol. The process results in the syn addition of a hydrogen and a hydroxyl group where the double bond had been. Hydroboration–oxidation is an ...

s. Like most dialkyl

boron hydride Diborane(6), commonly known as diborane, is the chemical compound with the formula . It is a highly toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has attr ...

s, it has a dimeric structure with bridging hydrides.

Reactions

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, beta-isoamylene, or trimethylethylene is an alkene hydrocarbon with the molecular formula C5H10. Used as a free radical scavenger in trichloromethane (chloroform) and dichloromethane (methylene chloride ...

with

diborane Diborane(6), commonly known as diborane, is the chemical compound with the formula . It is a highly toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has att ...

. The reaction stops at the secondary borane due to steric hindrance. Disiamylborane is relatively selective for terminal alkynes and alkenes vs internal alkynes and alkenes. Like most

, the addition proceeds in an anti-Markovnikov manner. It can be used to convert 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 n ...

s, into

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

s. The hydroboration process proceeds via an initial dissociation of the dimer.{{cite journal , doi=10.1021/jo00204a019 , title=Hydroboration kinetics. 11. A reinvestigation of the kinetics of hydroboration of representative alkenes with disiamylborane dimer. Conclusive evidence for the dissociation mechanism in the hydroboration of alkenes with dialkylborane dimers , date=1985 , last1=Chandrasekharan , first1=J. , last2=Brown , first2=Herbert C. , journal=The Journal of Organic Chemistry , volume=50 , issue=4 , pages=518–520

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 It can be prepared by base-catalyzed isomerization of 2,3-dimethyl-1-butene. Another route ...

Naming

The prefix ''disiamyl'' is an abbreviation for "di''-sec-''iso

amyl Amyl may refer to: * Amylum or starch, a carbohydrate ** Amylopectin, a polymer of glucose found in plants; one of two components of starch ** Amylose, a helical polymer made of α-D-glucose units; one of two components of starch * Pentyl, a fiv ...

", where ''sec''-isoamyl ("secondary isoamyl") is an archaic name for the 1,2-dimethylpropyl group (amyl being a obsolescent synonym of pentyl).

References

Alkylboranes Reagents for organic chemistry