[1,2]-Aryl migration in the synthesis of substituted indoles: scope, mechanism, and high throughput experimentation

des-Formylflustrabromine (dFBr): A Structure-Activity Study on Its Ability To Potentiate the Action of Acetylcholine at α4β2 Nicotinic Acetylcholine Receptors

The naturally occurring indole alkaloid des-formylflustrabromine (dFBr; 1) is one of the first agents shown to act as a selective positive allosteric modulator (PAM) at α4β2 nicotinic acetylcholine receptors (nAChRs). We previously deconstructed this agent to determine which of its structural features contribute to its actions and have identified an agent that might serve as the basis for a " working pharmacophore". Here, we elaborate the dFBr (1; EC₅₀ = 0.2 μM) structure to identify how various structural modifications impact its actions. Electrophysiological studies with Xenopus laevis oocytes identified several compounds with dFBr-like potency and one, the 5-bromo analogue of 1 (i.e., 5-bromo dFBr; 25; EC₅₀ = 0.4 μM), with more than twice the efficacy of 1 as a PAM at α4β2 nAChRs.

Indole-3-Carbonitriles as DYRK1A Inhibitors by Fragment-Based Drug Design

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a potential drug target because of its role in the development of Down syndrome and Alzheimer's disease. The selective DYRK1A inhibitor 10-iodo-11H-indolo[3,2-c]quinoline-6-carboxylic acid (KuFal194), a large, flat and lipophilic molecule, suffers from poor water solubility, limiting its use as chemical probe in cellular assays and animal models. Based on the structure of KuFal194, 7-chloro-1H-indole-3-carbonitrile was selected as fragment template for the development of smaller and less lipophilic DYRK1A inhibitors. By modification of this fragment, a series of indole-3-carbonitriles was designed and evaluated as potential DYRK1A ligands by molecular docking studies. Synthesis and in vitro assays on DYRK1A and related protein kinases identified novel double-digit nanomolar inhibitors with submicromolar activity in cell culture assays.

Nickel-catalyzed borylation of halides and pseudohalides with tetrahydroxydiboron [B2(OH)4]

Arylboronic acids are gaining increased importance as reagents and target structures in a variety of useful applications. Recently, the palladium-catalyzed synthesis of arylboronic acids employing the atom-economical tetrahydroxydiboron (BBA) reagent has been reported. The high cost associated with palladium, combined with several limitations of both palladium- and copper-catalyzed processes, prompted us to develop an alternative method. Thus, the nickel-catalyzed borylation of aryl and heteroaryl halides and pseudohalides using tetrahydroxydiboron (BBA) has been formulated. The reaction proved to be widely functional group tolerant and applicable to a number of heterocyclic systems. To the best of our knowledge, the examples presented here represent the only effective Ni-catalyzed Miyaura borylations conducted at room temperature.

Elusive metal-free primary amination of arylboronic acids: synthetic studies and mechanism by density functional theory

Herein, we disclose the first metal-free synthesis of primary aromatic amines from arylboronic acids, a reaction that has eluded synthetic chemists for decades. This remarkable transformation affords structurally diverse primary arylamines in good chemical yields, including a variety of halogenated primary anilines that often cannot be prepared via transition-metal-catalyzed amination. The reaction is operationally simple, requires only a slight excess of aminating agent, proceeds under neutral or basic conditions, and, importantly, can be scaled up to provide multigram quantities of primary anilines. Density functional calculations reveal that the most likely mechanism involves a facile 1,2-aryl migration and that the presence of an ortho nitro group in the aminating agent plays a critical role in lowering the free energy barrier of the 1,2-aryl migration step.

InCl3 mediated one-pot multicomponent synthesis, anti-microbial, antioxidant and anticancer evaluation of 3-pyranyl indole derivatives

A simple and convenient method for the one-pot three-component synthesis of 3-pyranyl indoles has been accomplished by tandem Knoevenagel-Michael reaction of 3-cyanoacetyl indole, various aromatic aldehydes and malononitrile catalyzed by InCl(3) in ethanol under reflux conditions. The newly synthesized 3-pyranyl indoles were evaluated for anti-microbial, antioxidant, and anticancer activities. Some of the compounds showed good anticancer activity against MCF-7 breast cancer cell lines on comparison with of standard drug.