Boranes, oxidation with

Borane, trihexyl-, 53, 77 Boranes, oxidation with H2O2,... 

Borane, bis(3-methyl-2-butyl)-, 53, 79 Botane, trihexyl-, 53,77 Boranes, oxidation with H, O, 50,90 52,59... 

BCl, BBr, and BI undergo exchange reactions to yield mixed boron hahdes. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr or BI (21)-... 

Difluoroalkenyl boranes, which are prepared in situ, are converted to difluoromethyl ketones by oxidation with hydrogen peroxide m alkaline media [720] (equation 107)... 

Strategy What is an immediate precursor of a primary alcohol " Perhaps a terminal alkene, which could be hydrated with non-Markovnikov regiochemistiy by reaction with borane Followed by oxidation with H2O2-... 

Neutral carboranes and boranes react with transition-metal complexes forming metallocarboranes or metalloboranes, respectively. However, most metallocarboranes and metalloboranes are prepared from transition-metal halides and anionic carborane and borane species ( 6.5.3.4) or by reacting metal atoms and neutral boranes and carboranes. These reactions are oxidative addition reactions ( 6.5.3.3). 

Alkyldimethylphosphine-boranes 74 underwent enantioselective deprotonation employing (-)-sparteine/s-BuLi, followed by oxidation with molecular oxygen [91, 92] in the presence of triethyl phosphite (Scheme 12) to afford moderate yields of enantiomerically enriched alkyl(hydroxymethyl)methylphosphine-bo-ranes 76, with 91-93% ee in the case of a bulky alkyl group and 75-81% ee in the case of cyclohexyl or phenyl groups [93]. Except for the adamantyl derivative (in which the ee increased to 99%), no major improvement in the ee was observed after recrystallization. 

As mentioned in Sect. 2.2, phosphine oxides are air-stable compounds, making their use in the field of asymmetric catalysis convenient. Moreover, they present electronic properties very different from the corresponding free phosphines and thus may be employed in different types of enantioselective reactions, m-Chloroperbenzoic acid (m-CPBA) has been showed to be a powerful reagent for the stereospecific oxidation of enantiomerically pure P-chirogenic phos-phine-boranes [98], affording R,R)-97 from Ad-BisP 6 (Scheme 18) [99]. The synthesis of R,R)-98 and (S,S)-99, which possess a f-Bu substituent, differs from the precedent in that deboranation precedes oxidation with hydrogen peroxide to yield the corresponding enantiomerically pure diphosphine oxides (Scheme 18) [99]. 

The reaction of 7-oxabenzonorbomadiene 95 with (-)-diisopinocamphenyl-borane (96) gave the corresponding trialkylborane which, on treatment with acetaldehyde, followed by oxidation with H202/Na0H, afforded (+)-(lR,2S,4R)-7-oxabenzonorbom-5-en-2-exo-ol (97) in 80 % yield and 100 % enantiomeric purity. ... 

Hydroboration-oxidation of alkenes preparation of alcohols Addition of water to alkenes by hydroboration-oxidation gives alcohols via anti-Markovnikov addition. This addition is opposite to the acid-catalysed addition of water. Hydrohoration is regioselective and syn stereospecific. In the addition reaction, borane bonds to the less substituted carbon, and hydrogen to the more substituted carbon of the double bond. For example, propene reacts with borane and THF complex, followed by oxidation with basic hydrogen peroxide (H2O2), to yield propanol. 

It is to be noted that boranes react with water in such a manner that the latter acts as oxidant, e.g. ... 

The C —B bond in /1,/f-difluoroalkenylboranes 1, which are prepared in situ, is oxidized with hydrogen peroxide in alkaline media the intermediate vinyl boranes are converted by immediate hydrolysis into difluoromethyl ketones 2.268... 

These data indicate that borane fuels have many props which are superior to those of JP-6. Comparison of the performance of a borane fuel with that of JP type, and using liq O as oxidizer, shows that a HEF increases the range of air-breathing engines or rockets by ca 50% over that obtd with a JP fuel in the same vehicle... 

Treatment of [4.S ]-4-/-butyl-l-mcthylcyclohcxcnc with borane-THF followed by oxidation with F Ch-NaOH gives a mixture of [ 1.S , 2.S ,5.S ]-5-/-butyl-2-methylcyclohcxan-1 -ol and [ 1 A,2A,5.S -5-/-butyl-2-methylcyclohexan-l-ol and no other diastereomers. There are two steps in this process—addition to give an organoborane and oxidation which cleaves the carbon-boron bond to an alcohol. 

The low yield observed in the isomerization of the 2,4,4-trimethylpent-2-ene (28) is because of the facile cyclization of the borane 30, with evolution of hydrogen, to produce a boron heterocycle 31. Oxidation of the reaction mixture provides... 

Reaction of a 5-alkoxy derivative with NaBD4 gave the 5,5-dideutero derivative exclusively <87JHC25l>. Reduction of the compounds (79) with borane in THF gave the amines (81), whose oxidation with DDQ in AcOH afforded the derivatives (80) <92JMC320>. 

Alkenylboronic acids and esters have been prepared by thermal or catalyzed hydroboration of 1-alkynes with catecholborane (HBcat), pinacolborane (HBpin), or dihaloboranes 41-43, followed by hydrolysis to boronic acids or alcoholysis to boronic esters. A convenient alternative to improve chemo- and regioselectivity is the hydroboration of alkynes with dialkylboranes. For selective removal of dummy groups, the oxidation of two cyclohexyl groups was conduced by treatment of l-alkenyl(dicyclohexyl)borane intermediates with Me3N-0 (Equation (7)).116 The... 

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