Enantioselective Synthesis of Spiroketals and Spiroaminals via Gold and Iridium Sequential Catalysis

Abstract

The enantioselective cascade reaction between racemic 2‐(1‐hydroxyallyl)phenols and alkynols/alkynamides was realized by using a gold and iridium sequential catalytic system. In this procedure, the in situ generated exocyclic vinyl ethers or enamides undergo the asymmetric allylation/spiroketalization with π‐ally‐Ir amphiphilic species, which provides an efficient and straightforward access to spiroketals and spiroaminals with excellent enantioselectivities. Moreover, racemic 2‐(1‐hydroxyallyl)anilines were also suitable in this reaction along with a kinetic resolution process, affording enantioenriched spiroaminals and 2‐(1‐hydroxyallyl)anilines in good yields. The synthetic utility of this method has been demonstrated by efficient enantioselective synthesis of the analogue of Paecilospirone.

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

“…Yang and Deng group reported a gold and iridium sequential‐catalyzed enantioselective cascade reaction of 2‐(1‐hydroxyallyl)phenols 1 with alkynols or alkynamides 2 or 3 (Scheme 1). [30] This in situ method produces exocyclic vinyl ethers or enamides 4 in 30–72 % yield with 94–99 % ee, which is then subjected to asymmetric allylation/spiroketalization with π ‐ally‐Ir amphiphilic species, allowing for quick and easy access to spiroketals and spiroaminals with high enantioselectivities. The screened optimized condition are 4 mol% [Ir(cod)Cl] 2 , 16 mol% ligand, 10 mol% PPh 3 AuCl, 1 equiv.…”

Direct Growth of Uniform Bimetallic Core‐Shell or Intermetallic Nanoparticles on Carbon via a Surface‐Confinement Strategy for Electrochemical Hydrogen Evolution Reaction

“…Supported bimetallic NPs are widely used in heterogeneous catalysis, wherein the structure/distribution of the active metal components (e.g., core/shell, Janus, and intermetallic compounds) is found of particular importance to its catalytic reactivity. [ 1–12 ] However, directly constructing structure‐regulable ultrafine bimetallic NPs on solid support was extremely challenging. [ 13–16 ] For instance, traditional techniques to synthesize core‐shell bimetallic NPs largely relied on wet chemistry.…”

Diastereo‐ and Enantioselective Synthesis of Bisbenzannulated Spiroketals and Spiroaminals by Ir/Ag/Acid Ternary Catalysis

“…In particular, the method toward such chiral bisbenzannulated [6,6]‐spiroketals still limited to the intramolecular spiroketalization reported by Ding [14a] and Dou [14b] . Recently, our group developed an Ir‐mediated oxidative addition [15] of readily available 2‐(1‐hydroxyallyl)phenol to generate a novel Ir‐π‐allyl‐oxa‐dipole, which was used for the enantioselective synthesis of benzo[ b ]oxocines [16a] and spiroketals [16b] . We envisioned that the bisbenzannulated [6,6]‐spiroketal could be synthesized through the intermolecular cascade allylation/spiroketalization reaction of in situ generated isochromenes with this Ir‐π‐allyl‐oxa‐dipole (Scheme 2b).…”