Rhodium-catalyzed regioselective direct C–H arylation of indoles with aryl boronic acids

Late-stage modification of complex drug: Base-controlled Pd-catalyzed regioselective synthesis and bioactivity of arylated osimertinibs

Achieving regioselective synthesis in complex molecules with multiple reactive sites remains a tremendous challenge in synthetic chemistry. Regiodivergent palladium-catalyzed C─H arylation of complex antitumor drug osimertinib with various aryl bromides via the late-stage functionalization strategy was demonstrated here. This reaction displayed a switch in regioselectivity under complete base control. Potassium carbonate (K2CO3) promoted the arylation of acrylamide terminal C(sp2)-H, affording 34 derivatives. Conversely, sodium tert-butoxide (t-BuONa) mediated the aryl C(sp2)-H arylation of the indole C2 position, providing 27 derivatives. The derivative 3r containing a 3-fluorophenyl group at the indole C2 position demonstrated similar inhibition of EGFRT790M/L858R and superior antiproliferative activity in H1975 cells compared to osimertinib, as well as similar antiproliferative activity in A549 cells and antitumor efficacy in xenograft mouse model bearing H1975 cells. This approach provides a "one substrate-multi reactions-multiple products" strategy for the structural modification of complex drug molecules, creating more opportunities for the fast screening of pharmaceutical molecules.

The crucial role of silver(I)-salts as additives in C-H activation reactions: overall analysis of their versatility and applicability

Transition-metal catalyzed C-H activation reactions have been proven to be useful methodologies for the assembly of synthetically meaningful molecules. This approach bears intrinsic peculiarities that are important to be studied and comprehended in order to achieve its best performance. One example is the use of additives for the in situ generation of catalytically active species. This strategy varies according to the type of additive and the nature of the pre-catalyst that is being used. Thus, silver(I)-salts have proven to play an important role, due to the resulting high reactivity derived from the pre-catalysts of the main transition metals used so far. While being powerful and versatile, the use of silver-based additives can raise concerns, since superstoichiometric amounts of silver(I)-salts are typically required. Therefore, it is crucial to first understand the role of silver(I) salts as additives, in order to wisely overcome this barrier and shift towards silver-free systems.

Solvent-controlled regioselective arylation of indoles and mechanistic explorations

A new reaction for the regioselective arylation of indoles at C2 or C3 positions achieved by adjusting the solvent and with P(O)tBu2 as an auxiliary group is reported. And the experimental results and DFT confirmed the process.

Recent advances in rhodium-catalyzed C(sp2)-H (hetero)arylation

Arylation is a common behaviour in organic synthesis for the construction of complex structures, especially the biaryls. Among those reported arylation procedures, transition-metal-catalyzed direct C(sp²)-H arylation has been rapidly developed in recent decades and has become a reliable alternative to traditional cross-coupling procedures using organometallic reagents. Great achievements in rhodium-catalyzed C(sp²)-H arylation have been witnessed during the last decade. Aryl halides, simple arenes, aryl boronic acids, arylsilanes, aryl aldehyde, aryl carboxylic acid, diazides, etc. were successfully utilized as arylating reagents under rhodium-catalyzed conditions. In this review, recent achievements in rhodium-catalyzed arylations through C(sp²)-H bond activation were summarized together with the mechanism discussions.

Transition metal-catalyzed C–H functionalizations of indoles

This review summarises a wide range of transformations on the indole skeleton, including arylation, alkenylation, alkynylation, acylation, nitration, borylation, and amidation, using transition-metal catalyzed C–H functionalization as the key step.

Visible-Light-Induced Decarboxylative Cyclization of 2-Alkenylarylisocyanides with α-Oxocarboxylic Acids: Access to 2-Acylindoles

An efficient and practical protocol for visible-light-induced decarboxylative cyclization of 2-alkenylarylisocyanides with α-oxocarboxylic acids has been developed, which afforded a broad range of 2-acylindoles in moderate to good yields. The reaction proceeds through a cascade of acyl radical addition/cyclization reactions under irradiation of an Ir³⁺ photoredox catalyst without external oxidants and features simple operation, scalability, a broad substrate scope, and good functional group tolerance.

Direct C–H bond activation: palladium-on-carbon as a reusable heterogeneous catalyst for C-2 arylation of indoles with arylboronic acids

We report a methodology for exclusive C-2 arylated indoles without the aid of any ligand or directing group in air.

Nickel-Catalyzed C(2)-H Arylation of Indoles with Aryl Chlorides under Neat Conditions

Nickel-catalyzed regioselective C(2)-H arylation of indoles and pyrroles with aryl chlorides is achieved under neat conditions. This method allows the efficient coupling of diverse aryl chlorides employing a user-friendly and inexpensive Ni(OAc)₂/dppf catalyst system at 80 °C. Numerous functionalities, such as halides, alkyl ether, fluoro-alkyl ether, and thioether, and substituted amines, including heteroarenes like benzothiazolyl, pyrrolyl, indolyl, and carbazolyl, are well tolerated under the reaction conditions. The preliminary mechanistic study highlights a single-electron transfer (SET) pathway for the arylation reaction.

Synthesis of 2-Arylindoles by Rhodium-Catalyzed/Copper-Mediated Annulative Coupling of N-Aryl-2-aminopyridines and Propargyl Alcohols via Selective C-H/C-C Activation

A versatile rhodium-catalyzed/copper-mediated C-H/C-C activation and cascade annulation reaction was described to form 2-arylindole derivatives. Highly selective C-C bond cleavage of γ-substituted tert-propargyl alcohols occurred, together with pyridine-directed ortho C(sp²)-H bond activation, affording a series of 2-arylindoles with yields up to 90%. Subsequent derivations were smoothly conducted to access polyfunctionalized 2-arylindoles, illustrating the potential applications of this method.

Transition metal-catalyzed site- and regio-divergent C–H bond functionalization

The regioselectivity of C–H functionalization reactions can be redirected to obtain regioisomeric products form the same starting materials.