Synthesis ofN-Alkylated Indolines and Indoles from Indoline and Aliphatic Ketones

Domino Aza-Michael-SNAr-Heteroaromatization Route to C5-Substituted 1-Alkyl-1H-Indole-3-Carboxylic Esters

A new synthesis of C5-substituted 1-alkyl-1H-indole-3-carboxylic esters is reported. A series of methyl 2-arylacrylate aza-Michael acceptors were prepared with aromatic substitution to activate them towards SNAr reaction. Subsequent reaction with a series of primary amines generated the title compounds. Initially, the sequence was expected to produce indoline products, but oxidative heteroaromatization intervened to generate the indoles. The reaction proceeded under anhydrous conditions in DMF at 23–90 °C using equimolar quantities of the acrylate and the amine with 2 equiv. of K2CO3 to give 61–92% of the indole products. The reaction involves an aza-Michael addition, followed by SNAr ring closure and heteroaromatization. Since the reactions were run under nitrogen, the final oxidation to the indole likely results from reaction with dissolved oxygen in the DMF. Substrates incorporating a 2-arylacrylonitrile proved too reactive to prepare using our protocol. The synthesis of the reaction substrates, their relative reactivities, and mechanistic details of the conversion are discussed.

Selective Iron Catalyzed Synthesis of N-Alkylated Indolines and Indoles

Whereas iron catalysts usually promote catalyzed C3-alkylation of indole derivatives via a borrowing-hydrogen methodology using alcohols as the electrophilic partners, this contribution shows how to switch the selectivity towards N-alkylation. Thus, starting from indoline derivatives, N-alkylation was efficiently performed using a tricarbonyl(cyclopentadienone) iron complex as the catalyst in trifluoroethanol in the presence of alcohols leading to the corresponding N-alkylated indoline derivatives in 31-99 % yields (28 examples). The one-pot, two-step strategy for the selective N-alkylation of indolines is completed by an oxidation to give the corresponding N-alkylated indoles in 31-90 % yields (15 examples). This unprecedented oxidation methodology involves an iron salt catalyst associated with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and a stoichiometric amount of t-BuOOH at room temperature.

Condensation-Based Methods for the C-H Bond Functionalization of Amines

This review aims to provide a comprehensive overview of condensation-based methods for the C-H bond functionalization of amines that feature azomethine ylides as key intermediates. These transformations are typically redox-neutral and share common attributes with classic name reactions such as the Strecker, Mannich, Friedel-Crafts, Pictet-Spengler, and Kabachnik-Fields reaction, while incorporating a redox-isomerization step. This approach provides an ideal platform to rapidly transform simple starting materials into complex amines.

The synthesis of N-benzoylindoles as inhibitors of rat erythrocyte glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase

Glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) play an important function in various biochemical processes as they generate reducing power of the cell. Thus, metabolic reprogramming of reduced nicotinamide adenine dinucleotide phosphate (NADPH) homeostasis is reported to be a vital step in cancer progression as well as in combinational therapeutic approaches. In this study, N-benzoylindoles 9a--9d, which form the main framework of many natural indole derivatives such as indomethacin and N-benzoylindoylbarbituric acid, were synthesized through three easy and effective steps as an in vitro inhibitor effect of G6PD and 6PGD. The N-benzoylindoles inhibited the enzymatic activity with IC₅₀ in the range of 3.391505 μM for G6PD and 2.19-990 μM for 6PGD.

Bismuth nitrate-promoted disproportionative condensation of indoles with cyclohexanone: a new-type azafulvenium reactivity of indole

The bismuth nitrate-promoted disproportionative condensation of indoles with cyclohexanone in one pot, to yield C3-cyclohexyl substituted indoles and 1,3-di(1H-indol-3-yl)benzene derivatives is reported for the first time.

A facile one-pot method to synthesise 2-alkylated indole and 2,2′-bis(indolyl)methane derivatives using ketones as electrophiles and their anion sensing ability

Indole derivatives are of great importance because of their biological activity and application in technology.