Organoboron compounds

Mikhaĭlov, B. M.; Vaver, V. A.

doi:10.1007/bf01160226

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“…The best-studied protonolysis of trialkylboranes by carboxylic acids is efficient at room temperature for the first alkyl group, but, due to the lower acidity of the newly formed borinic ester, further reactivity requires prolonged stirring or heating. The protonolysis of the third group occurs only with propionic acid in refluxing diglyme . Mineral acids can also form a complex with a trialkylborane and subsequently transfer a proton to the carbon atom.…”

Section: Introductionmentioning

confidence: 99%

Radical Chain Reduction of Alkylboron Compounds with Catechols

2011

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The conversion of alkylboranes to the corresponding alkanes is classically per-formed via protonolysis of alkylboranes. This simple reaction requires the use of severe reaction conditions, that is, treatment with a carboxylic acid at high temperature (>150 °C). We report here a mild radical procedure for the transformation of organoboranes to alkanes. 4-tert-Butylcatechol, a well-established radical inhibitor and antioxidant, is acting as a source of hydrogen atoms. An efficient chain reaction is observed due to the exceptional reactivity of phenoxyl radicals toward alkylboranes. The reaction has been applied to a wide range of organoboron derivatives such as B-alkylcatecholboranes, trialkylboranes, pinacolboronates, and alkylboronic acids. Furthermore, the so far elusive rate constants for the hydrogen transfer between secondary alkyl radical and catechol derivatives have been experimentally determined. Interestingly, they are less than 1 order of magnitude slower than that of tin hydride at 80 °C, making catechols particularly attractive for a wide range of transformations involving C-C bond formation.

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Section: Introductionmentioning

confidence: 99%