Acyl Migration versus Epoxidation in Gold Catalysis: Facile, Switchable, and Atom‐Economic Synthesis of Acylindoles and Quinoline Derivatives. (26th November 2019)

• Record Type: Journal Article
• Authors: Tian, Xianhai; Song, Lina; Farshadfar, Kaveh; Rudolph, Matthias; Rominger, Frank; Oeser, Thomas; Ariafard, Alireza; Hashmi, A. Stephen K.
• Is Part Of: Angewandte Chemie. Volume 132:Number 1(2020)
• Page Start: 479
• Page End: 486
• Publication Date: 2019-11-26
• Subjects: Acylmigration -- Anthranile -- Epoxidierungen -- Goldcarbene -- Goldkatalyse; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201912334
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: We report a switchable synthesis of acylindoles and quinoline derivatives via gold‐catalyzed annulations of anthranils and ynamides. α‐Imino gold carbenes, generated in situ from anthranils and an N, O‐coordinated gold(III) catalyst, undergo electrophilic attack to the aryl π‐bond, followed by unexpected and highly selective 1, 4‐ or 1, 3‐acyl migrations to form 6‐acylindoles or 5‐acylindoles. With the (2‐biphenyl)di‐ tert ‐butylphosphine (JohnPhos) ligand, gold(I) carbenes experienced carbene/carbonyl additions to deliver quinoline oxides. Some of these epoxides are valuable substrates for the preparation of 3‐hydroxylquinolines, quinolin‐3(4 H )‐ones, and polycyclic compounds via facile in situ rearrangements. The reaction can be efficiently conducted on a gram scale and the obtained products are valuable substrates for preparing other potentially useful compounds. A computational study explained the unexpected selectivities and the dependency of the reaction pathway on the oxidation state and ligands of gold. With gold(III) the barrier for the formation of the strained oxirane ring is too high; whereas with gold(I) this transition state becomes accessible. Furthermore, energetic barriers to migration of the substituents on the intermediate sigma‐complexes support the observed substitution pattern in the final product. Abstract : Katalysatorgesteuerte [3+2]‐ und [4+2]‐Anellierungen wurden zur Synthese von Acylindolen und Chinolinderivaten entwickelt. Sechs verschiedene Verbindungsklassen – darunter 6‐Acylindole 3, 5‐Acylindole 4, Chinolinoxide 5, 3‐Hydroxylchinoline 6, Chinolin‐3(4 H )‐one 7 und eine polycyclische Verbindung – wurden aus Anthranilen 1 und Ynamiden 2 durch selektive Acylmigration und Epoxidbildung über α‐Iminogoldcarben‐Zwischenprodukte synthetisiert.