Goldkatalysierte C‐H‐Anellierung von Anthranilen mit Alkinen: flexible, atomökonomische Synthese ungeschützter 7‐Acylindole

Abstract

Die goldkatalysierte C-H-Anellierung von Anthranilderivaten mit Alkinen erçffnet eine einfache,f lexible und atomçkonomische einstufige Route zu ungeschützten 7-Acylindolen. Über eine a-Iminogoldcarben-Zwischenstufe,d ie in einer intermolekularen Reaktion generiert wird, erfolgt eine ortho-Aryl-C-H-Funktionalisierung zur Zielverbindung.D ie Transformation zeichnet sich durche in breites Substratspektrum und milde Bedingungen aus.D arüber hinaus stellen die erhaltenen Indole eine vielseitige Plattform für den Aufbau verschiedenster Indolyl-Grundgerüste dar.

Regiodivergent Control in the Gold(I) Catalyzed Synthesis of 7‐Pyrazolylindoles from 1‐Propargyl‐1H‐benzotriazoles and Ynamides through α‐Imino Gold(I) Carbene Complexes

“…Thus, from Table 3 can be inferred that, under the reaction conditions, a phenyl ynamide raises both indoles in almost equimolecular amount (entry 4). However, the presence of electron-donating groups favours preferentially the formation of the 3-amidoindole compound 5 (entries [5][6][7][8][9]. Additionally, this effect correlates very well with the donation capability of the substituents, ranging from a low effect for the methyl group (entry 5) to an almost exclusive formation of regioisomer 5 in other cases (entries 7-9).…”

“…[5] In addition to the use of azides, other procedures involving intra-or intermolecular attacks to gold activated alkyne derivatives have been performed. Thus, pyridine-N-aminides, [6] 2H-azirine derivatives, [7] isoxazoles, [8] oxadiazoles, [9] dioxazoles, [10] indazoles [11] or directly from a gold-catalyzed decomposition of diazo compounds [12] have demonstrated to be alternatives. On the other hand, we have recently reported in this field an efficient procedure for the synthesis of 2-imidazolyl-1-pyrazolylbenzenes from propargylbenzotriazoles, alkynes and nitriles (Figure 1), [13] with the participation of isolable triazapentalenes as nucleophiles.…”

Highly Site Selective Formal [5+2] and [4+2] Annulations of Isoxazoles with Heterosubstituted Alkynes by Platinum Catalysis: Rapid Access to Functionalized 1,3‐Oxazepines and 2,5‐Dihydropyridines

“…[9] Notably, nonpolarized alkynes also underwent this transformation when MsOH (10 mol %) was used as an additive. This chemistry has also been aptly exploited in the synthesis of 3-aminopyrroles through the rhodium-catalyzed formal [3+2] annulation of 1,2,3-triazoles with isoxazoles by Tang and co-workers.…”

“…[8] Very recently, Hashmi and co-workers reported an elegant protocol for the synthesis of unprotected 7-acyl indoles through the gold-catalyzed CÀH annulation of anthranils with ynamides by a similar strategy (Scheme 1 b). [9] Notably, nonpolarized alkynes also underwent this transformation when MsOH (10 mol %) was used as an additive. This chemistry has also been aptly exploited in the synthesis of 3-aminopyrroles through the rhodium-catalyzed formal [3+2] annulation of 1,2,3-triazoles with isoxazoles by Tang and co-workers.…”

Highly Site Selective Formal [5+2] and [4+2] Annulations of Isoxazoles with Heterosubstituted Alkynes by Platinum Catalysis: Rapid Access to Functionalized 1,3‐Oxazepines and 2,5‐Dihydropyridines

“…[3,4] Hence, access to novel Pt carbenes is highly desirable, not only for the enrichment of platinum chemistry, but also because it may result in a selectivity switch for the construction of diverse intricate scaffolds. [9] Notably, nonpolarized alkynes also underwent this transformation when MsOH (10 mol %) was used as an additive. [8] Very recently, Hashmi and co-workers reported an elegant protocol for the synthesis of unprotected 7-acyl indoles through the gold-catalyzed CÀH annulation of anthranils with ynamides by a similar strategy (Scheme 1 b).…”