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Hydroboration–oxidation reaction is a two-step hydration reaction that converts an alkene into an alcohol. [1] The process results in the syn addition of a hydrogen and a hydroxyl group where the double bond had been. Hydroboration–oxidation is an anti-Markovnikov reaction, with
In the hydroboration reaction, diborane also reacts readily with alkenes to form trialkylboranes. This reaction pattern is rather general and the resulting alkyl borates can be readily derivatized, e.g. to alcohols. Although early work on hydroboration relied on diborane, it has been replaced by borane dimethylsulfide, which is more safely handled.
Formally, the reaction is an example of a group transfer reaction. However, an analysis of the orbitals involved reveals that the reaction is 'pseudopericyclic' and not subject to the Woodward–Hoffmann rules for pericyclic reactivity. Hydroboration of a terminal alkene to a trialkylborane, showing idealized image of the cyclic transition state.
Diborane reacts with alkenes to give alkylboranes, a process known as hydroboration: B 2 H 6 + 2 CH 2 =CHR → 2 BH 2 (CH 2 CH 2 R) B 2 H 6 + 4 CH 2 =CHR → 2 BH(CH 2 CH 2 R) 2 B 2 H 6 + 6 CH 2 =CHR → 2 B(CH 2 CH 2 R) 2. Alkyl and aryl boranes can also be produced by alkylation of chloroboranes and boronic esters.
The compound is commercially available as a solution in tetrahydrofuran and as a solid. 9-BBN is especially useful in Suzuki reactions. [6] [7] [8] Its highly regioselective addition on alkenes allows the preparation of terminal alcohols by subsequent oxidative cleavage with H 2 O 2 in aqueous KOH. The steric demand of 9-BBN greatly suppresses ...
It adds across alkenes to give organoboron compounds that are useful intermediates. [4] The following organoboron reagents are prepared from borane-THF: 9-borabicyclo[3.3.1]nonane, Alpine borane, diisopinocampheylborane. It is also used as a source of borane (BH 3) for the formation of adducts. [5]
Borane ammoniate, which is produced by a displacement reaction of other borane adducts, eliminates elemental hydrogen on heating to give borazine (HBNH) 3. [12] Borane adducts are widely used in organic synthesis for hydroboration, where BH 3 adds across the C=C bond in alkenes to give trialkylboranes: [13] (THF)BH 3 + 3 CH 2 =CHR → B(CH 2 CH ...
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 hydroboration, the addition proceeds in an anti-Markovnikov manner. [1] It can be used to convert terminal alkynes, into aldehydes.