Metal-free oxidative coupling of quinoxalin-2(1H)-ones with arylaldehydes leading to 3-acylated quinoxalin-2(1H)-ones

Abstract

A facile TBHP-mediated direct oxidative coupling of quinoxalin-2(1H)-ones with arylaldehydes has been developed under metal-free conditions. This method provided a convenient and efficient approach to various 3-acylated quinoxalin-2(1H)-ones from readily available starting materials with excellent regioselectivity. This reaction proceeded efficiently under mild conditions over a broad range of substrates and with functional group tolerance.

Copper‐Catalyzed Direct Oxidative Aroylations of Quinoxalinones with Methylarenes

“…A plausible mechanism based on these results and literature [14] reports is presented in Scheme 6. The copper(II) catalyst donates a single electron to TBHP for generating a copper(III) species and the tert‐ butoxyl radical.…”

Photoredox Catalyst Free, Visible Light‐Promoted C3−H Acylation of Quinoxalin‐2(1H)‐ones in Water

“…[12] Shortly after this discovery, the group of Yuan and Qu disclosed a TBHP-mediated direct 3-acylation of quinoxalin-2(1H)-ones by using arylaldehydes as the acyl radical precursors (Scheme 1b). [13] In a very recent contribution, the utilization of acyl hydrazine as acylating reagents to realize the direct 3-acylation of quinoxalin-2(1H)-ones was also realized by He et al (Scheme 1c). [14] Although encouraging improvements have been achieved in this field, the above-mentioned methods generally occurred under high reaction temperature (70~100°C) involving the utilization of transitionmetals in organic solvents.…”

Recent Developments in Direct C–H Functionalization of Quinoxalin-2(1H)-ones via Radical Addition Processes

“…Proposed mechanism for the direct C3 benzoylation of quinoxalin-2(1H)-one derivatives with -keto acids Soon after, Yuan and co-workers 26 reported an elegant method for the synthesis of C3-acylated quinoxalin-2(1H)one derivatives using aldehydes as acyl radical precursors. Among the different oxidants screened, tert-butyl hydroperoxide was found to be the best for this transformation.…”