Copper-Mediated Remote C-H Bond Chalcogenation of Quinolines on the C5 Position
An efficient and convenient method is developed for the remote C-H bond chalcogenation of 8-aminoquinoline scaffolds on the C5 position that is geometrically inaccessible. The protocol makes use of inexpensive CuBr2 as mediator and shows good t
An atom-economical and regioselective metal-free C-5 chalcogenation of 8-aminoquinolines under mild conditions
A general and simple metal-free protocol for expedient C-H functionalization leading to the regioselective generation of C-5 chalcogenated 8-aminoquinoline analogues in up to 90% yield at room temperature (25 °C) has been established. This methodology is an eco-friendly approach to the atom-economical utilization of diaryl/dialkyl chalcogenides for direct access to chalcogenated quinolines and is scalable to the gram scale without considerable decrease in the yield of the product. It represents a practical alternative to the existing metal-catalyzed functionalization of 8-aminoquinoline derivatives with broad functional group tolerance. The controlled experiments suggest that the reaction possibly proceeds through an ionic pathway at room temperature. Furthermore, the potentiality for the functionalization of free amines in chalcogenated-8-aminoquinolines provides an attractive perspective for further elaboration of the amine substituent through chemical manipulations. The applicability of the standardized method has been augmented through late-stage antimalarial drug diversification of primaquine analogues.
Copper-Catalyzed C5-H Sulfenylation of Unprotected 8-Aminoquinolines Using Sulfonyl Hydrazides
The synthesis of C5-sulfenylated 8-aminoquinolines using unprotected 8-aminoquinolines and sulfonyl hydrazides is achieved via the catalysis of CuI. The reactions are hypothesized to proceed via the Cu(I)-Cu(II)-Cu(I) catalytic processes induced by aerobic oxidation and single-electron transfer on the Cu(II)-8-aminoquinoline complex. This work discloses an unprecedented step-efficient method for the synthesis of C5-sulfenylated 8-aminoquinolines bearing a useful free NH2 group.
Visible-Light-Driven Halogen-Bond-Assisted Direct Synthesis of Heteroaryl Thioethers Using Transition-Metal-Free One-Pot C-I Bond Formation/C-S Cross-Coupling Reaction
An efficient protocol for the synthesis of thioether directly from heteroarenes has been developed in the presence of visible light in a one-pot manner at room temperature. This method involves two sequential reactions in a single pot where the formation of the iodinated heteroarene is followed by a transition-metal-free C-S coupling reaction. A wide range of heteroarene and thiol partners (including aliphatic thiols) have been used for the synthesis of thioethers. NMR studies and DFT calculations revealed the presence of a halogen bond between the thiolate anion (halogen bond acceptor) and iodoheteroarene (halogen bond donor). This halogen bonded complex on photoexcitation facilitates the electron transfer from the thiolate anion to the iodoheteroarene at room temperature.