Gold-Catalyzed Formal Hexadehydro-Diels–Alder/Carboalkoxylation Reaction Cascades

Abstract

A dual gold-catalyzed hexadehydro-Diels−Alder/carboalkoxylation cascade reaction is reported. In this transformation, the gold catalyst participated in the hexadehydro-Diels−Alder step, switching the mechanism from a radical type to a cationic one, and then the catalyst activated the resulting aryne to form an ortho-Au phenyl cation species, which underwent a carboalkoxylation rearrangement rather than the expected aryne−ene reaction.

Advancements in Gold‐Catalyzed Cascade Reactions to Access Carbocycles and Heterocycles: An Overview

“…Zi group described the gold‐catalyzed hexadehydro‐Diels‐Alder/carboalkoxylation cascade process of allylic‐ether‐tethered triyne 88 (Scheme 34). [71] The desired carboalkoxylation product 89 was formed in 46–85 % yield under optimized conditions i.e, 10 mol% IPrAuOTf in tetrahydrofuran at 0–60 °C for 0.5–24 h. With increasing the chain length of the terminal position, a six‐membered oxacycle formed in 80 % yield. F, Me, or MeO substituted substrates produced the required products with excellent regioselectivities.…”

Recent progress in the homogeneous gold-catalysed cycloisomerisation reactions

“…Multifunctional organic compound arenes have been studied for a long time to prepare complex natural compounds. 45 In 2021, Weiwei Zi 46 and co-workers reported the first hexadehydro-Diels-Alder/carbo alkoxylation reaction using IPrAuNTf 2 as a dual catalyst. In this method, the gold catalyst promotes the hexadehydro-Diels-Alder process, switches the reaction mechanism to the cationic species, and activates the resulting aryne moiety, which undergoes carboalkoxylation rearrangement (Scheme 37).…”

The Aryne Ene Reaction

“…A recent report from Zi and co-workers observed similar alkene ene reactivity of HDDA-generated arynes (Scheme 12). 36 Interestingly, the addition of a gold catalyst completely switched the reactivity of the system to favour an unprecedented carboalkoxylation of the aryne 60, via a postulated ortho-Au phenyl cation and subsequent 3,3-sigmatropic rearrangement, with no trace of the ene reaction product 59.…”