Abstract
Poly-substituted aromatic sulfur compounds are widely found in pharmaceuticals, agrochemicals and organic materials. However, the position that a sulfur moiety can be introduced to is largely restricted to a pre-functionalized site; otherwise, use of electronically biased substrates or auxiliary groups that direct catalysis is required. Here we report a general ortho thiolation of common aryl and heteroaryl iodides via palladium-norbornene cooperative catalysis. Using this approach, an aryl or alky sulfur moiety can be site-selectively introduced at the arene ortho position without using sterically or electronically biased substrates. The arene ipso functionalization is simultaneously achieved through Heck, Suzuki or Sonogashira termination. The reaction is enabled by a unique class of electrophiles in palladium-norbornene cooperative catalysis, which are sulfenamides derived from seven-membered lactams. The broad substrates scope and high chemoselectivity could make this method attractive for synthesis of complex sulfur-containing aromatic compounds.
Highlights
Poly-substituted aromatic sulfur compounds are widely found in pharmaceuticals, agrochemicals and organic materials
We report a Pd/NBE-catalyzed ortho thiolation of aryl iodides, which is enabled by sulfenamide-type electrophiles (Fig. 1c)
Developing a stable and reactive electrophilic thiolation agent would be a key for realizing the ortho thiolation reaction
Summary
Poly-substituted aromatic sulfur compounds are widely found in pharmaceuticals, agrochemicals and organic materials. We report a general ortho thiolation of common aryl and heteroaryl iodides via palladium-norbornene cooperative catalysis Using this approach, an aryl or alky sulfur moiety can be site-selectively introduced at the arene ortho position without using sterically or electronically biased substrates. A general method that siteselectively introduces sulfur functional groups to unbiased and unactivated arene positions would be highly attractive for preparing multi-substituted aromatic sulfur compounds This has motivated us to explore the approach using palladium/norbornene (Pd/NBE) cooperative catalysis. We report a Pd/NBE-catalyzed ortho thiolation of aryl iodides, which is enabled by sulfenamide-type electrophiles (Fig. 1c) This approach provides a general platform to introduce various sulfur moieties to the arene ortho positon and simultaneously install other functional groups at the arene ipso position. The generality, scability and high chemoselectivity could make this method attractive for preparing complex sulfur-containing aromatic compounds
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