title: Mechanistic and preparative studies of radical chain homolytic substitution reactions of N-heterocyclic carbene boranes and disulfides.
abstract: Reactions of 1,3-dimethylimidazol-2-ylidene-borane (diMe-Imd-BH3) and related NHC-boranes with diaryl and diheteroaryl disulfides provide diverse NHC-boryl monosulfides (diMe-Imd-BH2SAr) and NHC-boryl disulfides (diMe-Imd-BH(SAr)2). Heating in the dark with 1 equiv of disulfide favors monosulfide formation, while irradiation with 2 equiv disulfide favors disulfide formation. With heteroaryl disulfides, the NHC-borane in the primary NHC-boryl sulfide product migrates from sulfur to nitrogen to give new products with a thioamide substructure. Most substitution reactions are thought to proceed through radical chains in which homolytic substitution of a disulfide by an NHC-boryl radical is a key step. However, with electrophilic disulfides under dark conditions, a competing ionic path may also be possible.
authors.affiliation: Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Xiangcheng
authors.initials: X
authors.lastname: Pan
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Vallet
authors.forename: Stéphane
authors.initials: S
authors.lastname: Schweizer
authors.forename: Karim
authors.initials: K
authors.lastname: Dahbi
authors.forename: Bernard
authors.initials: B
authors.lastname: Delpech
authors.forename: Nicolas
authors.initials: N
authors.lastname: Blanchard
authors.forename: Bernadette
authors.initials: B
authors.lastname: Graff
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Geib
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Curran
authors.forename: Jacques
authors.initials: J
authors.lastname: Lalevée
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Lacôte
mesh_terms: D001880:Boranes / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure
chemical_list: D001880:Boranes; D004220:Disulfides; D005609:Free Radicals; D006571:Heterocyclic Compounds; C030011:carbene; D008697:Methane