Iron-catalyzed alkylation of carbazole derivatives via hydroarylation of styrenes

Lewis Acid-Mediated Regioselective Hydrofunctionalization of Styrenes with Isatins and Heterocycles

The ligand-free Lewis acid-mediated regioselective hydroamination and hydroarylation of styrenes have been successfully developed in the presence of isatins or heterocyclic aryl compounds such as benzothiophenes and benzofurans. The reactions tolerate a variety of functional groups and afford the corresponding products in moderate to good yields. Deuterium labeling experiments show that the functionalized hydrogen of styrenes was derived from the nitrogen-hydrogen of the substrates in the hydroamination. Preliminary mechanistic studies suggest that the reactions may be a radical or a carbocation process.

Palladium-catalyzed amidation of carbazole derivatives via hydroamination of isocyanates

The first amidation of carbazoles at the N9 position via palladium-catalyzed hydroamination of isocyanates is demonstrated. This simple, general and efficient method could deliver a wide range of carbazole-N-carboxamides in up to 99% yield. The salient features of this transformation include simple conditions with no need for a strong base, high chemo- and regio-selectivities and good functional group tolerance. In particular, this work-up-free and chromatography-free protocol is time-saving, cost-effective and user-friendly.

H2 O ⋅ B(C6 F5 )3 -Catalyzed para-Alkylation of Anilines with Alkenes Applied to Late-Stage Functionalization of Non-Steroidal Anti-Inflammatory Drugs

Anilines are core motifs in a variety of important molecules including medicines, materials and agrochemicals. We report a straightforward procedure that allows access to new chemical space of anilines via their para-C-H alkylation. The method utilizes commercially available catalytic H2 O ⋅ B(C6 F5 )3 and is highly selective for para-C-alkylation (over N-alkylation and ortho-C-alkylation) of anilines, with a wide scope in both the aniline substrates and alkene coupling partners. Readily available alkenes are used, and include new classes of alkene for the first time. The mild reaction conditions have allowed the procedure to be applied to the late-stage-functionalization of non-steroidal anti-inflammatory drugs (NSAIDs), including fenamic acids and diclofenac. The formed novel NSAID derivatives display improved anti-inflammatory properties over the parent NSAID structure.

Transition-metal-catalyzed C-H bond alkylation using olefins: recent advances and mechanistic aspects

Transition metal catalysis has contributed immensely to C-C bond formation reactions over the last few decades, and alkylation is no exception. The superiority of such methodologies over traditional alkylation is evident from minimal reaction steps, shorter reaction times, and atom economy while also allowing control over regio- and stereo-selectivity. In particular, hydrocarbonation of alkenes has grabbed increased attention due its fundamental ability to effectively and selectively synthesise a wide range of industrially and pharmaceutically relevant moieties. This review attempts to provide a scientific viewpoint and a systematic analysis of the recent developments in transition-metal-catalyzed alkylation of various C-H bonds using simple and activated olefins. The key features and mechanistic studies involved in these transformations are described briefly.

Boron-Catalyzed Hydroarylation of 1,3-Dienes with Arylamines

Catalytic hydroarylation reactions of conjugated dienes are achieved using tris(pentafluorophenyl)borane as a Lewis acid catalyst under mild reaction conditions. This new protocol shows a broad substrate scope for the highly regioselective functionalization of sterically hindered aniline derivatives. Experimental and extensive density functional theory mechanistic studies show that the complex of residual water and B(C₆F₅)₃ plays a crucial role in the aryl-assisted protonation of conjugated dienes, forming allyl cation intermediates that induce the facile electrophilic aromatic substitution of aniline substrates.