Dual gold/photoredox-catalyzed bis-arylative cyclization of chiral homopropargyl sulfonamides with diazonium salts: rapid access to enantioenriched 2,3-dihydropyrroles

Abstract

A novel dual gold/photoredox-catalyzed bis-arylative cyclization of chiral homopropargyl sulfonamides with diazonium salts has been developed, allowing the facile synthesis of various enantioenriched 2,3-dihydropyrroles in generally moderate to good yields with excellent enantioselectivities under very mild conditions without using any strong oxidants. The reaction is proposed to undergo an Au/Au redox cycle promoted by visible-light photoredox catalysis.

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…[269] Under the same reaction conditions, 2-[(trimethylsilyl)ethynyl]phenol could be convertedt o2,3-diarylbenzofurans. [271] Several recent studies have explored the advantages of combining photoredox catalyzed oxidation of Au I with classical Aucatalyzed cycloisomerization of alkynes (Scheme 53). The same group then applied their methodology to the synthesis of ad iverse array of bis(aryl)-substituted heterocyclesb yC ÀN, CÀS, and CÀSe bondforming cross-coupling reactions.…”

“…Fouquet et al and Gauchot and Scheme51. Dual Au and photoredox catalyzedbis-arylative C(sp)ÀC(sp 2 ) bond-forming cross-coupling reactionsi nvestigated by (a-e) Alcaide et al [269,270] and (f) Wang et al [271] Scheme53. Dual Au and photoredox catalyzedbis-arylative C(sp)ÀC(sp 2 ) bond-forming cross-coupling reactionsi nvestigated by (a-e) Alcaide et al [269,270] and (f) Wang et al [271] Scheme53.…”

“…employed Au/photoredox catalyzed diarylative heterocyclization routes for the enantioselective synthesis of as eries of 2,3-dihydropyrroles. [271] Several recent studies have explored the advantages of combining photoredox catalyzed oxidation of Au I with classical Aucatalyzed cycloisomerization of alkynes (Scheme 53). Fensterbank et al investigatedt he methodology for the intramolecular arylativec yclizationo fo-alkynylphenols with aryl diazonium salts to produce benzofuran derivatives.…”

“…Dual Au and photoredox catalyzedC ÀCcross-coupling of alkynes with aryl diazonium salts throughanarylative version of the Meyer-Schuster rearrangement, studied by (a) Gloriuse tal., [266] (b) Alcaide et al, [267] and (c) Shin et al [268] Scheme52. Dual Au and photoredox catalyzedbis-arylative C(sp)ÀC(sp 2 ) bond-forming cross-coupling reactionsi nvestigated by (a-e) Alcaide et al [269,270] and (f) Wang et al [271] Scheme53. Dual Au and photoredox catalyzedintramolecular( a) alkoxyarylation, [272] (b) amino-arylation, [273] and (c) ipso-arylation-cyclization [274] reactions of alkynes with aryl diazonium salts.…”

Metal-mediated synthesis of pyrrolines

“…Later, the same group reported an enantioenriched access to multisubstituted 2-pyrrolines 218 by a combination of gold catalysis and visible-light photoredox catalysis. 123 Using different chiral homopropargyl sulfonamides 216 and a variety of aryldiazonium salts 217 in the presence of Ph 3 P$AuCl and a visible light photocatalysts such Ru(bpy) 3 (PF6) 2 , and irradiating with 13 W white LEDs, a bis-arylative 5-endo-dig cyclization led to enantioenriched 2,3-dihydropyrroles with high enantiomeric excesses (96-99% ee) and moderate yields (54-89%) (Scheme 69). The proposed mechanism is an Au(I)/Au(III) redox cycle accomplished by visible-light photoredox catalysis, without using a strong oxidant, and accomplished in a mild and selective manner.…”