title: Radical chain reduction of alkylboron compounds with catechols.
abstract: 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.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Villa
authors.forename: Guillaume
authors.initials: G
authors.lastname: Povie
authors.forename: Philippe
authors.initials: P
authors.lastname: Renaud
mesh_terms: D000473:Alkanes / Q000737:chemistry; D000975:Antioxidants / Q000737:chemistry; D001880:Boranes / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry
chemical_list: D000473:Alkanes; D000975:Antioxidants; D001880:Boranes; D002396:Catechols; D010636:Phenols; C038096:tert-butylcatechol; C042329:phenoxy radical