Electroreductive Intermolecular Coupling of 4-Quinolones with Benzophenones: Synthesis of 2-Substituted 4-Quinolones

Abstract

The electroreductive coupling of 1-alkoxycarbonyl-4-quinolones with benzophenones in the presence of trimethylsilyl chloride gave adducts reacted at the 2-position of 4-quinolones as trimethylsilyl ethers. The adducts were transformed to 2-(diarylhydroxymethyl)-4-quinolones. The electroreduction of 1,3-diethoxycarbonyl-4-quinolones and polyhalogenated 3-alkoxycarbonyl-1-alkyl-4-quinolones with benzophenones also gave adducts reacted at the 2-position of 4-quinolones. On the contrary, the electroreductive coupling of 1,3-diethooxycarbonyl-8-methoxy-4-quinolones occurred at the 4-position of 4-quinolones to give 4-substituted quinolines.

Cathodic Electrolysis: Electroreductive Organic Synthesis

“…[22] The traditional nucleophilic reactions can be replaced by a promising alternative using highly reactive organometallic reagents such as Grignard reagents is by employing a mild electrochemical approach to generate ketyl radicals/anions for subsequent addition or crosscoupling. [22] In 2019, for instance, Kise and co-workers carried out a two-electron cathodic reduction of diaryl ketones using trimethylsilyl chloride (TMSCl) to hydrofunctionalize chromones [24] and 4-quinolones; [25] the TMS-protected alcohols or similar compounds thus formed are found to be capable of undergoing further different transformations to attain various functionalized structures.…”

Recent Advances in C(sp3)–C(sp3) and C(sp3)–C(sp2) Bond Formation through Cathodic Reactions: Reductive and Convergent Paired Electrolyses

“…Interestingly, the functionalization of 3-methylchromone and 3-arylchromone produced selectively the cis -adducts (Scheme ). Soon after, the authors extended this procedure to the C2-functionalizations of 4-quinolones …”

“…Soon after, the authors extended this procedure to the C2-functionalizations of 4-quinolones. 32 Baran and Minteer et al reported an electroreductive coupling between aliphatic ketones 61 and unactivated alkenes 62 for the synthesis of tertiary alcohols 63 in good yields. 33 The electrolysis was performed in an undivided cell using a zinc-based sacrificial anode and tin cathode.…”