Gold‐ and Indium‐Catalyzed Synthesis of 3‐ and 6‐Sulfonylindoles from ortho‐Alkynyl‐N‐sulfonylanilines

Abstract

Aufeinander folgende C‐N‐ und C‐S‐Verküpfungen durch intramolekulare Aminosulfonylierung: Die goldkatalysierte Reaktion der 2‐Alkinyl‐N‐sulfonylaniline 1 (R1=H) ergibt 3‐Sulfonylindole 2 in guten bis hohen Ausbeuten, die Umsetzung von 2‐Alkinyl‐6‐methoxy‐N‐sulfonylanilinen 1 (R1=MeO) in Gegenwart von InBr3 führt hingegen zu 6‐Sulfonylindolen 3 als Hauptprodukten (siehe Schema).

Diverse Reactivity in a Rhodium(III)‐Catalyzed Oxidative Coupling of N‐Allyl Arenesulfonamides with Alkynes

“…[14] We carried out cross-over experiments to probe the intermolecularity of the sulfonyl 1,3-shift (Scheme 3 c). [15,16] When an equimolar mixture of 4 ae and 4 bf was heated at 130 8C under the catalytic conditions, the four expected products 3 ae, 3 af, 3 be, and 3 bf were detected by GC in a 1.1 : 1.4 : 1 : 1.1 ratio, which is consistent with our proposed mechanism. An intermolecular 1,3-shift of Ts À in a pyrrole synthesis was also reported recently.…”

Diverse Reactivity in a Rhodium(III)‐Catalyzed Oxidative Coupling of N‐Allyl Arenesulfonamides with Alkynes

“…When 2,3diethylpyridine was treated with p-tolylsulfinic acid (TsH) under the standard conditions, none of the desired pyridine but only decomposition was detected (Scheme 3 a). [15,16] When an equimolar mixture of 4 ae and 4 bf was heated at 130 8C under the catalytic conditions, the four expected products 3 ae, 3 af, 3 be, and 3 bf were detected by GC in a 1.1 : 1.4 : 1 : 1.1 ratio, which is consistent with our proposed mechanism. A likely mechanism is proposed in Scheme 3 b: Dissociation of Ts À generates a carbocation, and an S N 1-type substitution affords an isomeric 2,3-dihydropyridine intermediate.…”

Cycloisomerization of 2‐Alkynylanilines to Indoles Catalyzed by Carbon‐Supported Gold Nanoparticles and Subsequent Homocoupling to 3,3′‐Biindoles

“…This role is not only due to the significance of the potential applications but also as a standard to calibrate the efficiency of a given method. [1,2] Despite the fact that the cycloisomerization of 2-alkynylanilines provides one of the most direct and atom-economical manners to assemble indoles, [3,4] there are still no examples of any general protecting-group-free direct catalytic method capable of effecting this transformation heterogeneously. [5] Yet, in homogeneous catalysis this transformation has been successfully performed with gold-based systems.…”