Metal‐Free Electrochemical Oxidative Dihalogenation of Quinolines on the C5 and C7 Positions Using N‐Halosuccinimides

Abstract

An efficient and convenient method for electrochemically oxidative dichlorination or dibromination of 8‐aminoquinolines on C5 and C7 positions using N‐halosuccinimides (NCS and NBS) as the halogen source was described. Substrates with various functional groups were transformed smoothly and the halogenated products were obtained in good to excellent yields. These transformations feature transition‐metal‐free, oxidant‐free, and short reaction time.

Electrochemical cascade reactions: an account of recent developments for this modern strategic tool in the arsenal of chemical synthesis

“…Substrates with various functional groups were transformed smoothly under the developed transition metal-and oxidant-free conditions to form the halogenated products in good to excellent yields (Scheme 119). 110 An electrochemical method for the synthesis of tripyrazolones 316 was developed via a three-component dehydrogenative trimerization of pyrazolones 315. In this approach, the C(sp 3 )-H bond of pyrazolones gets activated, leading to hydrogen evolution at the cathode under metal-and externaloxidant-free conditions.…”

“…Substrates with various functional groups were transformed smoothly under the developed transition metal- and oxidant-free conditions to form the halogenated products in good to excellent yields (Scheme 119). 110…”

Selective Electrochemical Halogenation of Functionalized Quinolone

“…Hence, it is highly desirable to seek eco-friendly and transition-metal-free protocols for the halogenation of biologically active fractions. Electrochemical radical halogenation of some aromatic hydrocarbons has been reported recently (Scheme b). – Thereinto, Mo demonstrated a general electrochemical strategy for the Sandmeyer halogenation of aryl diazonium salts. Jiang developed an electrochemically induced tandem reaction for selective N1-alkylation and C3-halogenation of indoles in 2019.…”

Remote selective decarboxylative difluoroarylmethylation of 8-aminoquinolines under transition metal-free conditions

“…Although many successful examples of constructing C–C and C–X (X = O, N, P, S etc .) bonds by direct C–H functionalization at the C2, 4 C5 5 and C7 6 positions of 8-aminoquinolines have been reported, efficient approaches to the C4 functionalization are still rare because it is relatively less electrophilic (more nucleophilic) and the reports only cover C–H allylation, arylation, and phosphonation (Scheme 1a). 7 Therefore, it is with urgency that practical and mild synthetic methods to achieve the C–H functionalization of 8-aminoquinoline at the C4 position are developed.…”