title: Polarity reversal catalysis in radical reductions of halides by N-heterocyclic carbene boranes.
abstract: Otherwise sluggish or completely ineffective radical reductions of alkyl and aryl halides by N-heterocyclic carbene boranes (NHC-boranes) are catalyzed by thiols. Reductions and reductive cyclizations with readily available 1,3-dimethylimidazol-2-ylidene borane and a water-soluble triazole relative are catalyzed by thiophenol and tert-dodecanethiol [C(9)H(19)C(CH(3))(2)SH]. Rate constants for reaction of the phenylthiyl (PhS•) radical with two NHC-boranes have been measured to be ~10(8) M(-1) s(-1) by laser flash photolysis experiments. An analysis of the available evidence suggests the operation of polarity reversal catalysis.
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Xiangcheng
authors.initials: X
authors.lastname: Pan
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lacôte
authors.forename: Jacques
authors.initials: J
authors.lastname: Lalevée
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Curran