Recent Advances in Visible-Light-Induced Reactions Involving N-Alkoxypyridinium Salts

doi:10.6023/cjoc202605015

Abstract

N-Alkoxypyridinium salts are characterized by structural stability and ease of preparation, and tunable reactivity. Under appropriate conditions, they undergo homolytic cleavage of the N—O bond to generate alkoxy radicals and pyridine derivatives. Owing to their dual role as alkoxy radical precursors and sources of heteroaryl fragments, these compounds have demonstrated distinctive synthetic value in radical-mediated organic transformations. In recent years, with the rapid development of visible-light catalysis and photoredox catalytic systems, radical transformations involving N-alkoxypyridinium salts have been continuously expanded, providing new strategies for synthetic research in related fields. This review summarizes recent advances in visible-light-induced reactions of N-alkoxypyridinium salts, with an emphasis on the major reaction modes of alkoxy radicals. Particular attention is paid to substrate scope, reaction mechanisms, synthetic applications, and methodological advantages. Future perspectives in this field are also discussed.

Key words: N-alkoxypyridinium salts, visible light, alkoxy radicals, photoredox, radical transformations

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Chaoyang Wang, Chao Pi, Xia Mi. Recent Advances in Visible-Light-Induced Reactions Involving N-Alkoxypyridinium Salts[J]. Chinese Journal of Organic Chemistry, 2026, 46(8): 2859-2891.

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Fig. & Tab. 30

Scheme 1. Transformation pathways of N-alkoxypyridinium salts under visible light

Scheme 2. Visible-light photoredox-catalyzed synthesis of benzophosphole oxides

Scheme 3. Visible-light-induced EDA complex-promoted α-C—H phosphonylation of N-aryl tertiary amines

Scheme 4. Visible-light-induced C-H silylation/hydroxymethylation of pyridine derivatives

Scheme 5. Visible-light-induced direct C—H phosphonylation of quinolinones and coumarins

Scheme 6. Visible-light-induced quinolinone-mediated site-selective C-H functionalization of pyridines

Scheme 7. Visible-light-excited quinolinone-containing substrate enabled divergent radical cyclization

Scheme 8. Metal-free photocatalytic trifluoromethylation/pyridination of unactivated alkenes

Scheme 9. Visible-light-induced site-selective C—H acylation of pyridines

Scheme 10. Visible-light-induced pyridylation of C—H and X—H bonds

Scheme 11. Photoredox-catalyzed azolation of benzylic C—H bonds

Scheme 12. Visible-light-induced construction of methylene-bridged bisheterocycles

Scheme 13. Photocatalytic N-alkoxypyridinium salt-mediated remote C—H bond pyridination

Scheme 14. Visible-light/copper cooperative catalysis for remote C—H functionalization mediated by N-alkoxypyridinium salts

Scheme 15. Visible-light-induced remote C—H functionalization of N-alkoxypyridinium salts for δ-substituted alcohols

Scheme 16. Visible-light/copper cooperative catalysis for remote C—H thiophosphorylation for δ-thiophosphate alcohols

Scheme 17. Photoexcited palladium-initiated remote desaturation of N-alkoxypyridinium salts

Scheme 18. Photoredox-catalyzed synthesis of oxepanes

Scheme 19. Photoredox-catalyzed remote C(sp3)—H sulfinylation

Scheme 20. Photocatalytic alkoxy radical-mediated anti-Markovnikov alkoxylation

Scheme 21. Visible-light-catalyzed tandem cyclization/pyridination for the construction of tetrahydrofuran scaffolds

Scheme 22. Visible-light-induced ortho-migration of pyridine ring for trifluoromethylation and pyridylation of alkenes

Scheme 23. Visible-light-induced carbon-pyridylation of alkenes via N-alkoxypyridinium salts

Scheme 24. Visible-light-catalyzed three-component tandem cyclization for the construction of dihydrobenzofuran scaffolds

Scheme 25. Photoredox-catalyzed functionalization of unbiased enals

Scheme 26. Photocatalytic alkoxypyridination of alkenes using N-alkoxypyridinium salts

Scheme 27. Visible-light-induced alkoxy radical-mediated trifunctionalization of alkenes for the construction of N,O-spiroaminals

Scheme 28. Photocatalytic synthesis of phosphates from N-alkoxypyridinium salts and phosphites

Scheme 29. Visible-light/NHC cooperative catalysis enabling tandem cyclization of N-vinyloxy pyridinium salts

Scheme 30. Photocatalytic β-scission of N-alkoxypyridinium salts for alkylation of pyridines

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