Gold‐Catalyzed Cascade Reaction of Diynamides with Allylic Alcohols: A Versatile Platform to Allenamide, 2‐Aminofuran and Bridged [2.2.2]Octadiene Derivatives

Abstract

Transition metal‐catalyzed divergent synthesis through alternation of the catalyst is appealing, as it provides an operationally simple way to access different valuable products, while using the same reactants as starting materials. Herein, a gold‐catalyzed cascade reaction of conjugated diynamides with allylic alcohols is described. By variation of the catalysts, substituted allenes and furans could be obtained selectively. Mechanistic studies indicate that, after the addition of allylic alcohol to gold‐activated diynamide, a [3,3]‐sigmatropic rearrangement would take place and lead to the formation of a common reactive intermediate, which would further convert to the final products selectively. Further variation of the structure of diynamides has unveiled an additional reaction sequence involving intramolecular Himbert arene/allene Diels‐Alder cycloaddition to afford a series of dearomatized products bearing bicyclo[2,2,2]octadiene core.

Green and rapid acid-catalyzed ynamide skeletal rearrangement and stereospecific functionalization with anisole derivatives

“…On the basis of the above mechanistic studies, previous literature data 1–9 and our previous studies on ynamides, 10,12 d a plausible mechanism is drawn in Scheme 3. First, the Brønsted acid initiates the reaction process by providing a proton (H + ) source on the alkyne in the compound 4-methyl- N -(phenylethynyl-2- 13 C)- N -(2-(phenylethynyl)phenyl)benzenesulfonamide ( 1a′ ) to produce intermediate A .…”

“…1 However, there are many challenges and problems facing synthetic chemists due to its complementary reactivities under radical, 2 ionic or acidic, 2 f ,3 and transition-metal-catalyzed reactions 4 due to the biased carbon–carbon (α and β) triple bond directly bind to the nitrogen atom bearing an electron-withdrawing functionality, which results in higher reactivity, unwanted by-products, and issues with chemo-, regio-, and stereospecificity. 1–4 Various research groups (Sahoo, 1 c ,2 d , f ,5 Ye, 1 b , f ,2 b ,3 b , d ,4 a Evano, 2 a ,6 Hashmi, 7 and many others 8 ) have remarkably utilized ynamides in the construction of various heterocyclic compounds with the help of transition metals, Brønsted acids or additives, depending on the selection of the starting material and reaction conditions. 1–8 In particular, the key reaction intermediates generated in ynamide reactions are keteniminium 2 f ,3 with electrophilic reagents and ketenimine 4 c ,9 under thermal conditions or with nucleophilic reagents.…”

“…1–4 Various research groups (Sahoo, 1 c ,2 d , f ,5 Ye, 1 b , f ,2 b ,3 b , d ,4 a Evano, 2 a ,6 Hashmi, 7 and many others 8 ) have remarkably utilized ynamides in the construction of various heterocyclic compounds with the help of transition metals, Brønsted acids or additives, depending on the selection of the starting material and reaction conditions. 1–8 In particular, the key reaction intermediates generated in ynamide reactions are keteniminium 2 f ,3 with electrophilic reagents and ketenimine 4 c ,9 under thermal conditions or with nucleophilic reagents. In addition, metal carbenes are generated when using transition metals 4 c and other specific types of reactions, such as cyclization 1 a ,4 c and cycloadditions.…”

Azobenzene-Integrated NHC Ligands: A Versatile Platform for Visible-Light-Switchable Metal Catalysis

“…To demonstrate the wider applicability of the azImBA ligands in photoswitchable Au­(I) catalysis, we further synthesized a gold­(I) tosylate catalyst, 16 ·AuOTs (for photoswitch properties, see Table S4). Compared to benzoate as the counterion, the tosylate anion possesses weaker coordination ability resulting in higher and broader catalytic activity, and thus, gold­(I) tosylate complexes have been described as potent catalysts for various gold-catalyzed transformations. − We applied 16 ·AuOTs as catalysts in the intramolecular hydroamination of alkynyl aniline 26 to indole 27 (Figure b; for conversion plot see Figure S205). , The reactions were carried out using a lower catalyst loading (2 mol % instead of 5 mol %) in deuterated tetrahydrofuran and in the absence of benzoic acid.…”