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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 Although early work on hydroboration relied on diborane, it has been replaced by borane dimethylsulfide, which is more safely handled.
The reaction was originally described by H.C. Brown in 1957 for the conversion of 1-hexene into 1-hexanol. [3] Hexanol synthesis. Knowing that the group containing the boron will be replaced by a hydroxyl group, it can be seen that the initial hydroboration step determines the regioselectivity. Hydroboration proceeds in an anti-Markovnikov manner.
This chemical reaction is useful in the organic synthesis of organic compounds. [1] Hydroboration produces organoborane compounds that react with a variety of reagents to produce useful compounds, such as alcohols, amines, or alkyl halides. The most widely known reaction of the organoboranes is oxidation to produce alcohols from alkenes.
BH 3 is a trigonal planar molecule with D 3h symmetry. The experimentally determined B–H bond length is 119 pm. [4] In the absence of other bases, it dimerizes to form diborane. Thus, it is an intermediate in the preparation of diborane according to the reaction: [5] BX 3 +BH 4 − → HBX 3 − + (BH 3) (X=F, Cl, Br, I) 2 BH 3 → B 2 H 6
9-Borabicyclo[3.3.1]nonane or 9-BBN is an organoborane compound. This colourless solid is used in organic chemistry as a hydroboration reagent. The compound exists as a hydride-bridged dimer, which easily cleaves in the presence of reducible substrates. [1] 9-BBN is also known by its nickname 'banana borane'. [2]
The complex can reduce carboxylic acids to alcohols and is a common route for the reduction of amino acids to amino alcohols [3] (e.g. valinol). It adds across alkenes to give organoboron compounds that are useful intermediates. [4]
Disiamylborane (bis(1,2-dimethylpropyl)borane) is an organoborane with the formula [((CH 3) 2 CHCH(CH 3)) 2 BH] 2 (abbreviation: Sia 2 BH). It is a colorless waxy solid that is used in organic synthesis for hydroboration–oxidation reactions. Like most dialkyl boron hydrides, it has a dimeric structure with bridging hydrides.
Lewis acids, such as triphenylboron (B(C 6 H 5) 3), speed elimination, increasing the overall reaction rate. [1] Nickel-based catalysts deactivate when they formation of dicyanonickel(II) species, which are unreactive toward alkenes. The dicyanide arises via two pathways (L = phosphite): [1] Ni(H)(CN)L 2 + HCN → Ni(CN) 2 L 2 + H 2