Regio- and Stereoselective Direct N-Alkenylation of Indoles via Pd-Catalyzed Aerobic Oxidation

Vinylation of N-Heteroarenes through Addition/Elimination Reactions of Vinyl Selenones

A new protocol for the synthesis of N-vinyl azoles using vinyl selenones and azoles in the presence of potassium hydroxide was developed. This reaction proceeded under mild and transition metal-free conditions through an addition/elimination cascade process. Both aromatic and aliphatic vinyl selenones and various mono-, bi- and tri-cyclic azoles can be tolerated and give terminal N-vinyl azoles in moderate to high yields. A plausible mechanism is also proposed.

Palladium-Catalyzed N-Alkenylation of N-Aryl Phosphoramidates with Alkenes

Versatile and concise Pd-catalyzed oxidative N-alkenylation of N-aryl phosphoramidates with alkenes is described in this study, a reaction that is of great significance but surprisingly unexploited. The transformation proceeds under mild reaction conditions, using O₂ as a green oxidant and TBAB as an effective additive. An efficient catalytic system allows a variety of drug-related substrates to participate in these transformations, which is of great interest in the drug discovery and development of phosphoramidates.

Palladium-Catalyzed Oxidative Amination of α-Olefins with Indoles

Herein we report the use of indoles, one of the most common nitrogen-containing heterocycles in FDA-approved drugs, as nucleophiles in the Pd-catalyzed aza-Wacker reaction. This N-functionalization of indoles is a Markovnikov selective olefin functionalization of simple alkenes using catalytic Pd(NPhth)₂(PhCN)₂ and O₂ as the terminal oxidant in the presence of catalytic Bu₄NBr. Various substituted indoles and alkenes are found to participate; 21 examples are presented with yields ranging from 41 to 97% isolated yield. Additionally, lactams and oxazolidinones are shown to participate under the reaction conditions. Mechanistic investigations suggest that the phthalimide ligand and Bu₄NBr additive slow undesired side reactions: indole decomposition and olefin isomerization, respectively.

Stereoselective Direct N-Trifluoropropenylation of Heterocycles with a Hypervalent Iodonium Reagent

The availability and synthesis of fluorinated enamine derivatives such as N-(3,3,3-trifluoropropenyl)heterocycles are challenging, especially through direct functionalization of the heterocyclic scaffold. Herein, a stereoselective N-trifluoropropenylation method based on the use of a bench-stable trifluoropropenyl iodonium salt is described. This reagent enables the straightforward trifluoropropenylation of various N-heterocycles under mild reaction conditions, providing trifluoromethyl enamine type moieties with high stereoselectivity and efficiency.

Nickel(II)-Catalyzed [3 + 2] Cycloaddition of Nitrones and Allenoates to Access N-Vinylindoles and N-Vinylpyrroles

A variety of N-vinylindoles and N-vinylpyrroles were prepared in moderate to good yields through the nickel(II)-catalyzed [3 + 2] cycloaddition of α,β-unsaturated nitrones with allenoates under mild reaction conditions. A rational mechanism for the formation of N-vinylindoles was proposed based on the ¹⁸O-labeled experiments and key intermediates detected by high-resolution mass spectrometry trace experiments. The present method highlights a nickel(II)-controlled cyclization, atom-economical reaction, broad substrate scope, good functional group tolerance, and high Z-stereoselectivity for the enamine bond.

Substrate-Controlled Regio- and Stereoselective Synthesis of ( Z)- and ( E)- N-Styrylated Carbazoles, Aza-carbazoles, and γ-Carbolines via Hydroamination of Alkynes

We report herein the substrate-controlled regio- and stereoselective hydroamination of carbazoles, aza-carbazoles, and γ-carbolines with functionalized aromatic as well as aliphatic alkynes in a KOH/DMSO system in good yields. The electronic effect of the substrates governs the stereochemistry of the product. Electron-donating alkynes provided ( Z)-stereoselective products, and electron-withdrawing alkynes provided ( E)-stereoselective products. This approach also provides an easy route for the synthesis of mono- and bis-hydroaminated product. The deuterium-labeling studies were also conducted to support the mechanistic pathway.

Visible-light promoted intermolecular halofunctionalization of alkenes with N-halogen saccharins

A simple and efficient visible-light promoted intermolecular haloamination and haloetherification of alkenes was reported.