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

Selective Electrochemical Halogenation of Functionalized Quinolone

This work describes an effective C3-H halogenation of quinoline-4(1H)-ones under electrochemical conditions, in which potassium halides serve as both halogenating agents and electrolytes. The protocol provides expedient access to different halogenated quinoline-4(1H)-ones with unique regioselectivity, broad substrate scope, and gram-scale synthesis employing convenient, environmentally friendly electrolysis, in an undivided cell. Mechanism studies have shown that halogen radicals can promote the activation of N-H bonds in quinolones.

Chemodivergent Tandem Radical Cyclization of Alkene-Substituted Quinazolinones: Rapid Access to Mono- and Di-Alkylated Ring-Fused Quinazolinones

Chemodivergent tandem radical cyclization offers exciting possibilities for the synthesis of structurally diverse cyclic compounds. Herein, we revealed a chemodivergent tandem cyclization of alkene-substituted quinazolinones under metal- and base-free conditions, this transformation is initiated by alkyl radicals produced from oxidant-induced α-C(sp3 )-H functionalization of alkyl nitriles or esters. The reaction resulted in the selective synthesis of a series of mono- and di-alkylated ring-fused quinazolinones by modulating the loading of oxidant, reaction temperature, and reaction time. Mechanistic investigations show that the mono-alkylated ring-fused quinazolinones is constructed by the key process of 1,2-hydrogen shift, whereas the di-alkylated ring-fused quinazolinones is mainly achieved through crucial steps of resonance and proton transfer. This protocol is the first example of remote second alkylation on the aromatic ring via α-C(sp3 )-H functionalization and difunctionalization achieved by association of two unsaturated bonds in radical cyclization.

Copper-catalyzed selective C5-H bromination and difluoromethylation of 8-aminoquinoline amides using ethyl bromodifluoroacetate as the bifunctional reagent

A simple and effective method for the copper-catalyzed selective C5-H bromination and difluoromethylation of 8-aminoquinoline amides with ethyl bromodifluoroacetate as the bifunctional reagent was developed. The combination of cupric catalyst and alkaline additive results in a C5-bromination reaction, whereas cuprous catalyst combined with silver additive results in the C5-difluoromethylation reaction. This method has a broad substrate scope and allows for easy and convenient access to desired C5-functionalized quinolones with good to excellent yields.

Metal-free regioselective mono- and poly-halogenation of 2-substituted indazoles

An unprecedented metal-free regioselective halogenation of 2H-indazoles has been revealed, which not only realized the highly selective synthesis of mono-halogenated products, but also completed poly-halogenations by fine tuning the reaction conditions. Various mono-/poly-/hetero-halogenated indazoles were obtained in moderate to excellent yields. Notably, this approach features environmentally friendly solvents, mild reaction conditions, simple execution and short reaction time.

Remote Selective Decarboxylative Difluoroarylmethylation of 8-Aminoquinolines under Transition Metal-Free Conditions

A facile transition metal-free decarboxylative C4 selective C-H difluoroarylmethylation of 8-aminoquinolines has been developed. This strategy proceeds under simple aqueous conditions and displays a broad substrate scope and excellent functional...