A Review on Sulfur-Directed C−H Bond Activation

Transition-metal-catalyzed C−H bond activation employing a directing group has been shown to be a powerful tool to access C−C or C−hetero bond formation. Oxygen and nitrogen atoms are commonly applied as the electron donor for these directing groups. In contrast, there are only a few studies on sulfur-containing groups, probably due to their toxicity to transition-metal catalysts. Nowadays, a large amount of C−H activation reactions directed by sulfur-containing auxiliary groups have been successfully achieved. As these groups can be facilely removed or modified in situ or in further steps, they are of great value in creative synthetic strategies. This paper reviews recent advances in the studies using thioether, thiol/thiophenol/disulfide, sulfoxide, and thiocarbonyl as directing groups for intermolecular C−H functionalizations as well as intramolecular oxidative annulations.