Gold-catalyzed heterocyclic syntheses through α-imino gold carbene complexes as intermediates

Abstract

This review reports a comprehensive compilation of gold-catalyzed heterocyclic synthesis by using α-imino gold carbene complexes as the proposed intermediates.

α‐Imino Gold Carbene Intermediates from Readily Accessible Sulfilimines: Intermolecular Access to Structural Diversity

“…The development of synthetic methods involving imino gold carbene intermediates to facilitate the synthesis of challenging heterocycles is an ongoing endeavor. [15] Chemists can benefit from exploiting such methodologies for rapid synthesiso rl atestage modification of biologically importantc ompounds. Under this principle, as eries of cyclic nitrenoid precursors, including 2H-azirines, [17] isoxazoles, [18] 1,2,4-oxadiazoles, [19] 1,4,2dioxazoles, [20] 4,5-dihydro-1,2,4-oxadiazoles, [21] 2,1-benzisoxazoles, [22] 1,2-benzisoxazoles, [23] pyrido[1,2-b]indazoles, [24a] and triazapentalenes [24b,c] have been developed for the direct introductiono fn itrogen-containing heterocyclic frameworks, whereas the corresponding gold carbenes generally underwent al imited number of transformations (Scheme 1A).…”

“…[6] Functionalized gold carbenes have been frequently proposed as highly reactive intermediates in such reactions. Generally, gold carbenei ntermediates areg enerated by decomposition of diazo compounds, [7] 1,2-acyloxy migration of propargylic esters, [8] cycloisomerization of 1,n-enynes or [9] enynones, [10] ring-opening reaction of cyclopropenes, [11] dual activation of 1,5-diynes, [12] retro-Buchnerr eaction of cycloheptatrienes, [13] and gold-catalyzed oxygen, [14] nitrene [15] as well as carbene [16] transfer reactions. Among these modes, the generation of highly reactive gold carbene intermediates through gold-catalyzed group-transfer to CCt ripleb onds and subsequent diverse evolutions has experienced significant attention in the last decade.…”

AgNTf2-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

“…A tentative mechanism for the formation of 5-amino-1 H -pyrrole-3-carboxamide 10aa is provided in Scheme 5 [21,31–32]. Initial activation of ynamide 4a by silver catalyst can afford the Ag complex A , which can isomerize to the keteniminium ion intermediate B .…”

“…The generation of α-imino gold carbene intermediates in gold-catalyzed reactions of alkynes has been widely studied in recent years [21–30]. In 2015, Ye and co-workers, as pioneers, developed this chemistry with the employment of isoxazole nucleophiles in gold-catalyzed formal [3 + 2] cycloaddition reaction of ynamides [31–32], and zinc-catalyzed the reaction of ynol ethers [33], giving the respective multi-substituted pyrrole derivatives efficiently (Scheme 2) [34–35].…”

Gold-Catalyzed Complementary Nitroalkyne Internal Redox Process: A DFT Study

“…In this manuscript, we document the DFT calculations on the [Au]catalysed complementary nitroalkyne redox process that leads to α-oxo gold carbenes B and C, especially focusing on the energies associated with oxygen transfer and carbene transfer. This has been undertaken considering the importance of gold catalyzed processes that proceed through the α-imino and/or α-oxo gold carbenes and their promising applications in the heterocyclic synthesis (Aguilar and Santamaría, 2019;Zhang, 2014). These processes in general proceed through the carbene and/or nitrene transfer from the [Au]-centre (Ye, 2020).…”