Gold‐catalyzed [4+2] Annulations of Dienes with Nitrosoarenes as 4 π Donors: Nitroso‐Povarov Reactions

Abstract

This work reports the first success of the nitroso-Povarovreaction, involving gold-catalyzed [4+ +2] annulations of nitrsoarenes with substituted cyclopentadienes.I nt his catalytic sequence,n itrosoarenes presumably attackg old-pdienes by a1 ,4-addition pathway,g enerating allylgold nitrosonium intermediates to complete an intramolecular cyclization. Acyclic dienes are also applicable substrates,and affording oxidative nitroso-Povarov products.

Catalytic Asymmetric Aza‐Diels‐Alder Reaction: Pivotal Milestones and Recent Applications to Synthesis of Nitrogen‐Containing Heterocycles

“…Recently, Liu and co‐authors proposed a conceptually different type of [4+2] cycloaddition between nitrosoarenes 111 and cyclopentadienes, in which the former serve as 4π‐electron components and the latter as 2π‐counterparts. The authors managed to implement both racemic [151] and enantioselective versions of the reaction (nitroso‐Povarov reaction) [152] . Taking into account that labile cyclopentadiene derivatives readily undergo self‐dimerization, the authors employed 1‐allenyl‐4‐enes 115 as convenient precursors that could readily convert to diene substrates under the gold catalysis prior to cycloaddition (Scheme 43).…”

Electrochemically Tuned Oxidative [4+2] Annulation and Dioxygenation of Olefins with Hydroxamic Acids

“…Until very recently, Liu reported the first nitroso‐Povarov reaction of nitrosobenzenes and substituted cyclopentadienes using vinylallenes as the substrates under co‐catalysis of gold and silver (Scheme 1 b). [6b] Although the elegant work has been reported, it still requires noble metals and structurally special alkenes and does not apply to ordinary alkenes such as styrenes. Thus, the development of practical [4+2] protocol toward benzo[c][1,2]oxazine by exploring new counterpart of nitrosobenzene to react with abundant simple alkenes is urgent demanded.…”

Gold-Catalyzed Hydroalkoxylation/Povarov Reaction Cascade of Alkynols with N-Aryl Imines: Synthesis of Tetrahydroquinolines

“…In addition, the gold-catalyzed Povarov reaction followed by ring expansion has been reported by Liu. 8 Inspired by these advances, together with our interests in gold-catalyzed alkyne transformations, 16 herein, we disclose our recent results of one-pot gold(I)-catalyzed [4 + 2] annulation of alkynols with N -aryl imines or in situ generated iminium that afforded the tricyclic adducts in good to high yields (Scheme 1c). The gold catalyst features a dual function in this cascade reaction, which first catalyzed the intramolecular hydroalkoxylation of alkynols to form the dihydrofuran species and promoted the Povarov reaction at a later stage with high stereoselectivity.…”