Visible-Light-Promoted C2 Selective Arylation of Quinoline and Pyridine N-Oxides with Diaryliodonium Tetrafluoroborate

Abstract

A protocol of visible-light-promoted C2 selective arylation of quinoline and pyridine N-oxides, with diaryliodonium tetrafluoroborate as an arylation reagent, using eosin Y as a photocatalyst for the construction of N-heterobiaryls was presented. This methodology provided an efficient way for the synthesis of 2-aryl-substituted quinoline and pyridine N-oxides. This strategy has the following advantages: specific regioselectivity, simple operation, good functional group tolerance, and high to moderate yields under mild conditions.

Visible‐Light‐Induced C2 Alkylation of Heterocyclic N‐Oxides with N‐Hydroxyphthalimide Esters under Metal‐Free Conditions

“…Control experiments demonstrated that the base, photocatalyst and visible light were all essential for this transformation (entries [15][16][17]. Finally, the reactions could also proceed smoothly under irradiation with 18 W green light or white light (entries [18][19]. Comparing to most established methods in the literatures, [11,[14][15]17] this reaction protocol is more advantageous because it can avoid the use of extra oxidant.…”

“…[17] Very recently, Song disclosed the Eosin Y-catalyzed selective C2 arylation of heterocyclic N-oxides with diaryliodonium tetrafluoroborate using 1,4-benzoquinone as the additive (Scheme 1d). [18] As aliphatic carboxylic acids derivatives, N-hydroxyphthalimide (NHPI) esters have attracted considerable attentions and were commonly used as efficient alkyl electrophiles in alkyl coupling reactions. [19] NHPI esters are stable and readily available compounds derived from the corresponding carboxylic acids with NHPI under standard coupling conditions.…”

Diaryliodoniums Salts as Coupling Partners for Transition-Metal Catalyzed C- and N-Arylation of Heteroarenes

“…From this point of view, photoredox chemistry involving radical intermediates is discussed here. Since the breakdown of Sanford in 2012 who reported a photoredox palladium/iridium-catalyzed C-H arylation with diaryliodonium reagents under mild conditions [98], support for the feasibility of these photocatalytic reactions with heteroarenes is provided by few reports [99][100][101][102][103][104]. Room-temperature, visible-light photocatalysis-promoted transformations of diaryliodonium salts were described by Chatani in 2013 [99].…”

Recent Advances in the Synthesis of C2‐Functionalized Pyridines and Quinolines Using N‐Oxide Chemistry

“…Visible‐light‐promoted non‐deoxygenative arylation of pyridine and quinoline N ‐oxides has been realized with diaryliodonium tetrafluoroborate using Eosin Y as a photocatalyst [107] . Transition‐metal‐free arylation of N ‐oxides has also been achieved via a Reissert‐type mechanism.…”

“…Visible-light-promoted non-deoxygenative arylation of pyridine and quinoline N-oxides has been realized with diaryliodonium tetrafluoroborate using Eosin Y as a photocatalyst. [107] Transition-metal-free arylation of Noxides has also been achieved via a Reissert-type mechanism. In 2015, Wu's group described a basepromoted cross-dehydrogenative coupling between quinoline N-oxides and 1,3-azoles 268 under air (Scheme 80).…”