The regioselective C5 halogenation of quinolines using sodium halides under transition metal-free conditions

Visible Light Mediated External Oxidant Free Selective C5 Bromination of 8‐Aminoquinoline Amides under Ambient Conditions

“…Highly efficient C5 bromination was developed by Xu, Wang and coworkers just by using NBS under aqueous conditions in 15 mins (Scheme b (VII)) . Using K 2 S 2 O 8 as oxidant and bromide as bromine source, Zhang group (NaBr), Ghosh group (TBAB) and Sun group (LiBr) reported this reaction almost simultaneously (Scheme b (VIII), (IX)&(X)). The combination of photoredox and iron catalysis was applied by Wu, Yang, Wu and coworkers in this transformation (Scheme b (XI)) .…”

Regio‐Selective C−H Halogenation of 8‐Amido‐Quinolines under Transition Metal Free Conditions

“…reported the transition metal free oxidative bromination and chlorination of 8‐amino quinoline using oxone as oxidant and with excess (4 equivalent) sodium halides as halogenating agent . Very recently, Sodium halides as the halogen sources under transition metal‐free conditions reported by Zhang and co‐workers afforded the corresponding halogenated products in moderate to good yields . However the limitation of these above mentioned reports are mostly use of transition metal catalyst, in some cases use of excess halogenating reagent, rarely atom economical, sometimes harsh reaction condition, lack of site selectivity and versatility of halogenation.…”

Room‐Temperature C‐H Bromination and Iodination with Sodium Bromide and Sodium Iodide Using N‐Fluorobenzenesulfonimide as an Oxidant

“…disclosed an efficient strategy for aromatic halogenation with hydrogen halides (HBr or HI) using DMSO as the sole oxidant, but elevated temperature was required (Scheme a) . Several groups also utilized sodium or potassium halides as X + precursor with inorganic salts or peroxide as the oxidant, or through photocatalytic strategy (Scheme b) . Yet these reactions either suffered from limited substrate scope,, or required specific apparatus such as assistance of mechanical milling or ultrasound sonication ,.…”

“…Several groups also utilized sodium or potassium halides as X + precursor with inorganic salts or peroxide as the oxidant, or through photocatalytic strategy (Scheme b) . Yet these reactions either suffered from limited substrate scope,, or required specific apparatus such as assistance of mechanical milling or ultrasound sonication ,. We envisaged that, if a more powerful oxidant is discovered, the effectiveness and generality of this transition‐metal‐free oxidative C−H halogenation with sodium halides would be considerably improved.…”