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. 2022 Apr 29;12(20):12235-12241.
doi: 10.1039/d2ra00753c. eCollection 2022 Apr 22.

Regioselective C-3-alkylation of quinoxalin-2(1 H)-ones via C-N bond cleavage of amine derived Katritzky salts enabled by continuous-flow photoredox catalysis

Gandhari Kishor  1   2 , Vankudoth Ramesh  1   2 , Vadithya Ranga Rao  1   2 , Srihari Pabbaraja  1   2 , Praveen Reddy Adiyala  1   2
Affiliations

Regioselective C-3-alkylation of quinoxalin-2(1 H)-ones via C-N bond cleavage of amine derived Katritzky salts enabled by continuous-flow photoredox catalysis

Gandhari Kishor et al. RSC Adv. .

Abstract

An efficient, transition metal-free visible-light-driven continuous-flow C-3-alkylation of quinoxalin-2(1H)-ones has been demonstrated by employing Katritzky salts as alkylating agents in the presence of eosin-y as a photoredox catalyst and DIPEA as a base at room temperature. The present protocol was accomplished by utilizing abundant and inexpensive alkyl amine (both primary and secondary alkyl) and as well as this a few amino acid feedstocks were converted into their corresponding redox-active pyridinium salts and subsequently into alkyl radicals. A wide variety of C-3-alkylated quinoxalin-2(1H)-ones were synthesized in moderate to high yields. Further this environmentally benign protocol is carried out in a PFA (Perfluoroalkoxy alkane) capillary based micro reactor under blue LED irradiation, enabling excellent yields (72% to 91%) and shorter reaction times (0.81 min) as compared to a batch system (16 h).

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. C-3-alkylation of quinoxalin-2(1H)-one derivatives in the reported works and this work.
Scheme 2
Scheme 2. Scale-Up experiment and synthetic application.
Scheme 3
Scheme 3. Control experiments.
Scheme 4
Scheme 4. Plausible mechanistic pathway.
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