Visible-light-induced, copper(i)-catalysed C-N coupling between o-phenylenediamine and terminal alkynes: one-pot synthesis of 3-phenyl-2-hydroxy-quinoxalines

Abstract

Visible-light-initiated aerobic direct C-N coupling between o-phenylenediamines and terminal acetylenes was performed using simple copper(I) chloride as a catalyst for the synthesis of quinoxaline derivatives. The current method works well for a wide range of electron rich as well as electron poor group-substituted o-phenylenediamines and phenylacetylenes. The key component in the reaction is the direct photo-excitation of in situ generated copper arylacetylide (λ(abs) = 420-480 nm). Moreover, as compared to the literature reports (thermal process), the current photochemical method is simple, mild, high yielding, and more viable towards the construction of biologically important quinoxaline derivatives from easily accessible raw materials, without the need of ligands and strong oxidants.

Photoredox Catalysis with Metal Complexes Made from Earth‐Abundant Elements

“…With ortho-phenylenediamines( 117)i nsteado fa nilines as reactionp artnersf or terminal alkynes, the methodologyi ntroduced by Hwanga nd co-workers gave rapid access to quinoxalines (118)( Scheme 29 c). [64] As in the prior studies, aC u I phenylacetylide complex is likely ak ey intermediate, and the reactionproceeds wellw ith o-phenylenediamines bearing electron-donating or electron-withdrawing substituents. In combination with ar ange of possible terminal alkyner eaction partners, the facile one-pot synthesis of av ariety of different 3phenyl-2-hydroxy-quinoxalines was feasible.…”

“…[63] c) One-potsynthesis of 3-phenyl-2-hydroxy-quinoxalines. [64] Scheme30. a) One-step regioselective synthesis of functionalized indoles.…”

“…b) Oxidative coupling of 2‐aminopyridine to alkynes yielding pyridyl amides . c) One‐pot synthesis of 3‐phenyl‐2‐hydroxy‐quinoxalines …”

“…With ortho ‐phenylenediamines ( 117 ) instead of anilines as reaction partners for terminal alkynes, the methodology introduced by Hwang and co‐workers gave rapid access to quinoxalines ( 118 ) (Scheme c) . As in the prior studies, a Cu I phenylacetylide complex is likely a key intermediate, and the reaction proceeds well with o ‐phenylenediamines bearing electron‐donating or electron‐withdrawing substituents.…”

Visible light-induced transition metal-catalyzed transformations: beyond conventional photosensitizers

“…It should be noted that the authors previously implemented a similar strategy toward synthesis of quinoxalines involving Cu-photocatalysis. 20 …”