Hydroboration alkylborane formation

In the oxidation stage of hydroboration-oxidation, alkylboranes are converted into alkyl borates, which are hydrolyzed to alcohols. It has b n suggested that the formation of the borates involves the reagent HOO. ... 

Although water, in some cases, has undergone addition across the C-C double bond in a vinylcyclopropane under acidic, - neutral, " and basic " - aqueous conditions, e.g. formation of 2, the reaction has more often been performed using a two-step procedure. Most frequently used was a one-pot synthesis consisting of hydroboration followed by oxidation with hydrogen peroxide/sodium hydroxide. The alkylboranes, formed in the first step, can be isolated. - The first step has generally been carried out using diborane in tetrahydrofuran 398,410,430,745,852,1025,1590,1609,1793,1833.1877-1884 9-borabi-... 

Purpose. The oxidation of an alkene to an alcohol is investigated via the in situ formation of the corresponding trialkylborane, followed by the oxidation of the carbon-boron bond with hydrogen peroxide. The conditions required for hydroboration (a reduction) of unsaturated hydrocarbons are explored. Alkylboranes are particularly useful synthetic intermediates for the preparation of alcohols. The example used in this experiment is the conversion of 1-octene to 1-octanol in which an anti-Markovrukov addition to the double bond is required to yield the intermediate, trioctylborane. Since it is this alkyl borane that subsequently undergoes oxidation to the alcohol, hydroboration offers a synthetic pathway for introducing substituents at centers of unsaturation that are not normally available to the anti-Markovnikov addition reactions that are based on radical intermediates. 

Boron.—Hydroboration and B—C Bond Formation. There have been several efforts aimed at stabilizing those alkylboranes with established synthetic use but limited stability (CH2NMe2)2 (TMED) complexes of BH2R and BHR2 are air... 

The addition of borane to alkenes is stereospecifically cis and leads to the formation of tri-alkylboranes. These may be oxidized to alcohols using the anion of hydrogen peroxide. Overall addition of water is achieved, in a c/s-stereospecific, anti-Markovnikov manner. Hydroboration/oxidation of alkynes gives ketones, after tautomerization of the enol formed. c/s-Dihydroxylation of alkenes is accomplished with catalytic OSO4 plus an oxidant such as NMO or K3[Fe(CN)g]. This contrasts with the formation of frans-diols by epoxidation of alkenes followed by the opening of the epoxide with hydroxyl ion. 

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