Photo-free electron donor-acceptor complexes driven divergent synthesis of thioethers and thioimidate esters with aryldiazonium salts and thiols/thiophenols

A catalyst- and photo-free strategy for the divergent synthesis of thioethers and thioimidate esters from thiophenols/thiols and aryldiazonium salts has been developed. The reaction pathway is precisely controlled by temperature and bases. The electron donor-acceptor (EDA) complex-initiated cross-coupling of aryl and thiyl radicals was achieved at 0 °C in the presence of a base. The EDA complex initiated cascade aryl radical addition to acetonitrile, followed by coupling with thiyl radical, was realized at 70 °C in the absence of base. Both transformations feature broad substrate scope, good functional group tolerance, large-scale synthesis, along with metal- and photo-free conditions. Detailed mechanistic studies indicated that the corresponding radicals can be generated precisely and react in situ to avoid self-coupling under catalyst- and photo-free conditions.