Synthesis of γ,δ-Unsaturated Esters and Amides via Au(I)-Catalyzed Reactions of Aryl Ynol Ethers or Ynamides with Allylic Alcohols

Polarized alkynes such as ynol ethers and ynamides have attracted much attention due to their inherent unique reactivity. Herein, we report Au(I)-catalyzed hydroalkoxylation/Claisen rearrangement cascade reactions of aryl ynol ethers and ynamides with allylic alcohols. At the first stage (hydroalkoxylation) of this cascade reaction, attack of allylic alcohols to aryl ynol ethers or ynamides occurs at the α-position of the polarized alkynes in an entirely regioselective manner. Claisen rearrangement of the resulting adducts subsequentially takes place to give γ,δ-unsaturated esters or amides, respectively. The [Au(IPr)NTf2] catalyst is most effective for this reaction, and the reaction proceeds under mild conditions (in the case of aryl ynol ether: in THF, 60 °C; in the case of ynamides: in toluene, 80 °C) in an atom-economical way.

Access to Substituted Indenol Ethers via a Regioselective Intermolecular Carbopalladation Cascade

Alkyne carbopalladation reactions represent a powerful approach to generating multiple new C–C bonds and substituted alkenes, however regioselectivity is often challenging for intermolecular variants. By utilizing ynol ethers as polarized alkynes we observe complete regiocontrol of migratory insertion with Pd–Ar species. A Heck reaction was used to turn-over the catalytic cycle by intercepting the vinyl-Pd adduct of carbopalladation with a pendant alkene. When using <i>o</i>-iodo styrenes substrates the resulting products are oligosubstituted 1-indenol ethers with defined stereochemistry based on the initial alkene geometry. By blocking β-hydride elimination we demonstrated C–H and C–C reductive elimination steps for catalyst turnover. Herein we report the optimization of reaction conditions, scope, and alternative termination steps.

Access to Substituted Indenol Ethers via a Regioselective Intermolecular Carbopalladation Cascade

Alkyne carbopalladation reactions represent a powerful approach to generating multiple new C–C bonds and substituted alkenes, however regioselectivity is often challenging for intermolecular variants. By utilizing ynol ethers as polarized alkynes we observe complete regiocontrol of migratory insertion with Pd–Ar species. A Heck reaction was used to turn-over the catalytic cycle by intercepting the vinyl-Pd adduct of carbopalladation with a pendant alkene. When using <i>o</i>-iodo styrenes substrates the resulting products are oligosubstituted 1-indenol ethers with defined stereochemistry based on the initial alkene geometry. By blocking β-hydride elimination we demonstrated C–H and C–C reductive elimination steps for catalyst turnover. Herein we report the optimization of reaction conditions, scope, and alternative termination steps.

Benign catalysis with zinc: atom-economical and divergent synthesis of nitrogen heterocycles by formal [3 + 2] annulation of isoxazoles with ynol ethers

A zinc-catalyzed formal [3 + 2] annulation of isoxazoles with ynol ethers has been developed, leading to the atom-economical and divergent synthesis of 2-alkoxyl 1H-pyrroles and 3H-pyrroles, respectively.

Accessing 4-oxy-substituted isoquinolinones via C–H activation and regioselective migratory insertion with electronically biased ynol ethers

The rhodium-catalyzed C–H activation and annulation with ynol ethers to directly provide 4-oxy substituted isoquinolinones is reported.