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Review
. 2024 Dec 9;16(3):1041-1070.
doi: 10.1039/d4sc07491b. eCollection 2025 Jan 15.

Photocatalytic regioselective C-H bond functionalizations in arenes

Jun Hu  1 , Suman Pradhan  1 , Satyadeep Waiba  1 , Shoubhik Das  1
Affiliations
Review

Photocatalytic regioselective C-H bond functionalizations in arenes

Jun Hu et al. Chem Sci. .

Abstract

The direct functionalization of C-H bonds has revolutionized the field of synthetic organic chemistry by enabling efficient and atom-economical modification of arenes by avoiding prefunctionalization. However, the inherent challenges of inertness and regioselectivity in different C-H bonds, particularly for distal positions, necessitate innovative approaches. In this aspect, photoredox catalysis by utilizing both transition metal and organic photocatalysts has emerged as a powerful tool for addressing these challenges under mild reaction conditions. This review provides a comprehensive overview of recent progress in regioselective C-H functionalization in arenes via photocatalysis. Emphasizing the strategies for achieving ortho-, meta-, and para-selectivity, we explore the mechanistic insights, catalyst designs, and the novel methodologies that have expanded the scope of C-H bond functionalization. This discussion aims to offer valuable perspectives for advancing the field and developing more efficient and sustainable synthetic methodologies.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Fig. 1
Fig. 1. (A) General mechanism of photoredox catalysis. (B) Photoredox catalysis mediated arene C–H bond activation strategies.
Fig. 2
Fig. 2. Summary of this review.
Scheme 1
Scheme 1. Photoinduced ortho-C–H arylation with aryldiazonium salts.
Scheme 2
Scheme 2. Photoinduced ortho-C–H arylation with aryl halides.
Scheme 3
Scheme 3. Photoinduced ortho-C–H benzylation and allylation.
Scheme 4
Scheme 4. Photoinduced directed ortho-C–H olefination.
Scheme 5
Scheme 5. Photoinduced ortho-C–H acylation.
Scheme 6
Scheme 6. Photoinduced ortho-C–H borylation.
Scheme 7
Scheme 7. Photoinduced ortho-C–H alkynylation.
Scheme 8
Scheme 8. Photoinduced ortho-C–H alkylation from α-bromoketones.
Scheme 9
Scheme 9. Photoinduced ortho-C–H trifluoromethylation.
Scheme 10
Scheme 10. Photoinduced ortho-C–H phosphonylation.
Scheme 11
Scheme 11. Photoinduced ortho-C–H nitration.
Scheme 12
Scheme 12. Synthesis of benzothiazoles by photoinduced ortho-C–H thiolation.
Scheme 13
Scheme 13. Synthesis of indoles by ortho-C–H cyclization.
Scheme 14
Scheme 14. Synthesis of coumarins by ortho-C–H cyclization.
Scheme 15
Scheme 15. Synthesis of carbazoles by intramolecular ortho-C–H amination.
Scheme 16
Scheme 16. Photoinduced ruthenium-catalyzed meta-C–H alkylation with alkyl halides.
Scheme 17
Scheme 17. Site-selective coupling of remote C(sp3)–H/meta-C(sp2)–H bonds enabled by a Ru catalyst.
Scheme 18
Scheme 18. Photoinduced template mediated Pd-catalyzed meta-oxygenation of arenes.
Scheme 19
Scheme 19. NHC and organic photoredox-catalyzed meta-selective acylation of electron-rich arenes without directing group assistance.
Scheme 20
Scheme 20. Para-selective C–H bond halogenation of arenes.
Scheme 21
Scheme 21. Para-selective C–H bond functionalization of arenes.
Scheme 22
Scheme 22. Para-selective C–H bond trifluoromethylation of arenes.
Scheme 23
Scheme 23. Para-selective C–H difluoromethylation of arenes.
Scheme 24
Scheme 24. Para-selective C–H bond trifluoromethylation of benzamide.
Scheme 25
Scheme 25. Para-selective C–H bond functionalization of unprotected phenols.
Scheme 26
Scheme 26. Para-selective C–H bond alkylation of unprotected anilines.
Scheme 27
Scheme 27. Para-selective C–H bond alkylation of arenes.
Scheme 28
Scheme 28. Para-selective C–H bond alkenylation of arenes.
Scheme 29
Scheme 29. Para-selective C–H bond amination of arenes.
None
Jun Hu
None
Suman Pradhan
None
Satyadeep Waiba
None
Shoubhik Das
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