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. 2022 Dec 7;12(54):34831-34836.
doi: 10.1039/d2ra05078a. eCollection 2022 Dec 6.

Copper-promoted direct sulfenylation of C1-H bonds in 4-aryl pyrrolo[1,2- a]quinoxalines

Thuy T Ca  1   2   3 , Khanh T M Le  1   2 , Son N T Phan  1   2 , Huy H Nguyen  1   2 , Huy X Le  1   2 , Nam T S Phan  1   2 , Tung T Nguyen  1   2
Affiliations

Copper-promoted direct sulfenylation of C1-H bonds in 4-aryl pyrrolo[1,2- a]quinoxalines

Thuy T Ca et al. RSC Adv. .

Abstract

Methods for direct functionalization of C(sp2)-H bonds in pyrrolo[1,2-a]quinoxalines have witnessed emerging development over the last decade. Herein we report a new tactic to afford a selective sulfenylation of 4-aryl pyrrolo[1,2-a]quinoxalines with diaryl disulfides. The reactions proceeded in the presence of a copper catalyst and potassium iodide promoter. Functionalities including nitro, ester, amide, methylthio, and halogen groups were all tolerated. Our method offers a convenient route to obtain highly substituted pyrrolo[1,2-a]quinoxalines-based thioethers in moderate to good yields.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. Scope of pyrrolo[1,2-a]quinoxalines. Reagents and conditions: 1b–1o (0.1 mmol), diphenyl disulfide 2a (0.05 mmol), CuCl2 (0.03 mmol), KI (0.05 mmol), DMSO (1 mL), 120 °C, 24 h, under air. Yields are isolated yields. aDiphenyl disulfide 2a (0.075 mmol) was used.
Scheme 2
Scheme 2. Sulfenylation of pyrrolo[1,2-a]quinoxaline C1–H bond in the presence of C4–H bond.
Scheme 3
Scheme 3. Sulfenylation of pyrrolo[1,2-a]quinoxaline C–H bonds with di(hetero)aryl disulfides. Reagents and conditions: pyrrolo[1,2-a]quinoxalines 1q/1a (0.1 mmol), disulfides (0.075 mmol for 2b–2c, 0.05 mmol for 2d–2f), CuCl2 (0.03 mmol), KI (0.05 mmol), DMSO (1 mL), 120 °C, 24 h, under air. Yields are isolated yields.
Scheme 4
Scheme 4. Mechanistic consideration. Reagents and conditions: (eqn (1)) 1a (0.1 mmol), CuCl2 (0.03 mmol), KI (0.05 mmol), DMSO (1 mL), 120 °C, 24 h, under air; (eqn (2)) 1a (0.1 mmol), 2a (0.05 mmol), CuCl2 (0.03 mmol), KI (0.05 mmol), 1,1′-diphenylethylene (0.2 mmol), DMSO (1 mL), 120 °C, 24 h, under air.
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