Imidazolium Salt Catalyzed para -Selective Halogenation of Electron-Rich Arenes
A highly para-selective halogenation of arenes bearing coordinating groups in the presence of a dimidazolium salt as a catalyst is reported. A series of electron-rich p-haloarenes were prepared in good yields and good to excellent selectivities. We also propose a plausible mechanism for the catalytic reaction.
Complementary Site-Selective Halogenation of Nitrogen-Containing (Hetero)Aromatics with Superacids
Site-selective functionalization of arenes that is complementary to classical aromatic substitution reactions remains a long-standing quest in organic synthesis. Exploiting the generation of halenium ion through oxidative process and the protonation of the nitrogen containing function in HF/SbF5, the chlorination and iodination of classically inert Csp2?H bonds of aromatic amines occurs. Furthermore, the superacid-promoted (poly)protonation of the molecules acts as a protection, favoring the late-stage selective halogenation of natural alkaloids and active pharmaceutical ingredients.