HAT-Mediated Electrochemical C(sp²)–H Acylation of Quinolines with Alcohols

Abstract

Herein, an electrochemical hydrogen atom transfer (HAT) strategy for C­(sp2)–H formylation of electron-deficient quinolines and isoquinolines is described. The cheap methanol acts as a formyl source with a catalytic amount of N-hydroxyphthalimide (NHPI) as the hydrogen atom transfer (HAT) catalyst. The advantages of this reaction are transition-metal-catalyst- and chemical-oxidant-free conditions, and the protocol could also be applied to the direct C­(sp2)–H acetylation or propionylation of quinolines.

Synthesis of Acyl Cyclopentaquinolinones through Simultaneous Construction of the Heterocyclic Scaffold and Introduction of the Acyl Group

“…Based on the above-described background, it is reasonable to deduce that incorporating an acyl unit onto the cyclopentaquinolinone scaffold might create new molecules potentially boasting synergetic biological activities, unique functional properties and enriching organic reactivity. So far, the most frequently used methods for the synthesis of acyl heterocyclic compounds include transition metal (TM)-catalyzed carbonylative coupling, Friedel–Crafts acylation, radical acylation, etc. − While these classical methods are generally effective and reliable, some of them still suffer from tedious multistep procedures to prepare the required heterocyclic substrates, corrosive catalysts, precarious organometallic reagents, or generation of harmful halide byproducts. Therefore, the development of more concise and sustainable methods for the synthesis of acyl cyclopentaquinolinone derivatives from simple and readily accessible acyclic substrates remains as a challenging task for the synthetic community.…”