Expedient synthesis of tetrasubstituted pyrroles via a copper-catalyzed cascade inter-/intramolecular cyclization of 1,3-enynes carry a nitro group with amines

Abstract

Various tetrasubstituted pyrroles/pyrazoles have been prepared from nitro-substituted 1,3-enynes with aromatic amines/hydrazines via a copper-catalyzed cascade aza-Michael addition, cyclization and aromatization at room temperature. This protocol is also effective for the synthesis of tetrasubstituted pyrazoles in high yields.

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

“…Subsequently, Punniyamurthy and co-workers also described the copper-catalyzed cascade cyclization of 2-nitro-1,3-enynes 34 to tetrasubstituted pyrroles 39 ( Scheme 14 ) [ 58 ]. Through screening the conditions, the Cu(OTf) 2 -promoted (5 mol %) annulation addition reaction of 2-nitro-1,3-enynes 34 and amines was carried out smoothly in THF at room temperature under air.…”

Recent Advances on Pyrrole Synthesis through Different Annulation Modes

“…Other than the strategies above, N1 unit related [4＋1] mode also could go through intermediates that have been used in the [5＋0] cyclization strategy. In 2015, a copper-Scheme 24 Oxalic acid promoted reaction of carbohydrates and primary amines catalyzed addition/cyclization cascade via a homopropargyl amine intermediate was developed by Punniyamurthy et al [48] affording 3-nitro substituted pyrroles in good yields (Scheme 25).…”

Recent developments in the group-1B-metal-catalyzed synthesis of pyrroles

“…25 This reaction started from the aza-Micheal addition of amines with enynes, which was followed by a Intramolecular 5-endo-dig cyclization to form five-membered heterocycles. Finally, the five-membered heterocycles were converted to target pyrroles through aromatization.…”