Mechanistic and preparative studies of radical chain homolytic substitution reactions of N-heterocyclic carbene boranes and disulfides.

Xiangcheng Pan , Anne-Laure Vallet , Stéphane Schweizer , Karim Dahbi , Bernard Delpech (1) , Nicolas Blanchard , Bernadette Graff , Steven J Geib , Dennis P Curran , Jacques Lalevée , Emmanuel Lacôte

1 ICSN - Institut de Chimie des Substances Naturelles

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.

Domaines: Chimie organique

Xiangcheng Pan, Anne-Laure Vallet, Stéphane Schweizer, Karim Dahbi, Bernard Delpech, et al.. Mechanistic and preparative studies of radical chain homolytic substitution reactions of N-heterocyclic carbene boranes and disulfides.. Journal of the American Chemical Society, 2013, 135 (28), pp.10484-91. ⟨10.1021/ja403627k⟩. ⟨hal-00853043⟩