Boranes oxidation with NaOH

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 dialkenylchloroboranes undergo the usual reactions of vinylic boranes, e.g., protonolysis with acetic acid gives olefins, oxidation with alkaline hydrogen peroxide provides the corresponding carbonyl compounds. However, the most useful reactions of these compounds are their ready conversion to the stereochemically pure (E, Z)-1,3-dienes by the Zweifel reaction with I2-NaOH 37>107.108> and into the symmetrical (E,E)- 1,3-dienes, 09 0), mono-olefins 1U) and 1,4-dienes (Chart 10). 

The borane is obtained h rjjci Diels-Alder reactions. Tha be effected at 25-85° with nvarled 1 on oxidation (H2O2, NaOH) afford TsOH at 55° afford 1.4-oclohev t... 

An environmentally benign and simple versatile method for hydroboration-oxidation of alkenes, dienes and alkynes imder microwave irradiation has been explored by Jayakumar et al. (2008). They carried out a simple and facile hydrob-oration-oxidation of alkenes by N,N-dimethylaniline-borane using microwave irradiation. Hydroboration of various alkenes with N,N-dimethylaniline-borane was carried out in dry THF under specially designed microwave apparatus. It was designed to accommodate magnetic stirrer and refluxing condenser with mercury bubbler. Hydroboration was followed by oxidation with HjO /NaOH, which resulted in the formation of corresponding alcohols in 90-95% yield. 

A soln. of tri-n-hexylborane in propionitrile containing tetraethylammonium iodide as supporting electrolyte electrolyzed 1 hr. at room temp, under Ng in an undivided cell with Pt-plate electrodes, then oxidized 2 hrs. with 30%-H2O2 and 3 N NaOH 2-methyloctanonitrile. Y 80% based on borane consumed. F. e. s. Y. Takahashi et al., Chem. Lett. 1975, 523 a-alkylation of aliphatic nitro compds. s. Synthesis 1976, 616 organic electrosynthesis, review s. L. L. Miller and E. Kariv, Ann. Reports. Med. Chem. 12, 309 (1977). 

Sym. ketones. A soln. of cyclopentene in diglyme allowed to react with a soln. of borane in tetrahydrofuran, stirred 1 hr. at room temp., tetrahydrofuran removed by distillation under reduced pressure, water added, heated to 100°, flushed with GO, stirred, after 2.5 hrs. when GO-absorption has ceased ice-cooled and oxidized below 35° with HgOg/NaOH dicyclopentyl ketone. Y 90%. 

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