Recent trends in the chemistry of Sandmeyer reaction: a review

Discovery of Potent and Selective Covalent Inhibitors of HER2WT and HER2YVMA

HER2 overexpression and amplification have been identified as oncogenic drivers, and the development of therapies to treat tumors harboring these markers has received considerable attention. Activation of HER2 signaling and subsequent cell growth can also be induced by HER2 mutations, including the common YVMA insertion in exon 20 within the kinase domain. Enhertu is currently the only approved treatment for HER2 mutant tumors in NSCLC. TKIs tested in this space have suffered from off-target activity, primarily due to EGFRWT inhibition or attenuated activity against HER2 mutants. The goal of this work was to identify a TKI that would provide robust inhibition of oncogenic HER2WT and HER2 mutants while sparing EGFRWT activity. Herein, we describe the development of a potent, covalent inhibitor of HER2WT and the YVMA insertion mutant while providing oral bioavailability and avoiding the inhibition of EGFRWT.

A Comprehensive Review on Benzofuran Synthesis Featuring Innovative and Catalytic Strategies

Benzofurans have intrigued both pharmaceutical researchers and chemists owing to the medicinal usage of their derivatives against copious disease-causing agents (i.e., bacteria, viruses, and tumors). These heterocyclic scaffolds are pervasively encountered in a number of natural products and drugs. The ever-increasing utilization of benzofuran derivatives as pharmaceutical agents persuaded the chemists to devise novel and facile methodological approaches to assemble the biologically potent benzofuran nucleus. This review summarizes the current developments regarding the innovative synthetic routes and catalytic strategies to procure the synthesis of benzofuran heterocycles with their corresponding mechanistic details, reported by several research groups during 2021-2023.

Recent Advancement on the Indirect or Combined Alternative Thiocyanate Sources for the Construction of S-CN Bonds

The process of thiocyanation is a notable chemical conversion owing to the extensive range of applications associated with thiocyanate compounds in the field of organic chemistry. In past centuries, the thiocyanation reaction incorporated metal thiocyanates or thiocyanate salts as sources of thiocyanate, which are environmentally detrimental and undesirable. In recent literature, there have been numerous instances where combined or indirect alternative sources of thiocyanate have been employed as agents for thiocyanation, showcasing their noteworthy applications. The present literature review focuses on elucidating the ramifications associated with the utilization of indirect or combined alternative sources of thiocyanate in various thiocyanation reactions.

Bromine-mediated strategy endows efficient electrochemical oxidation of amine to nitrile

Conventional methods for nitrile synthesis bring inherent environmental risks due to their reliance on oxidants and harsh reaction conditions. Meanwhile, direct electrooxidation of amines to nitriles suffers from low current density. In this study, we propose an innovative indirect electrooxidation strategy for nitrile formation, mediated by Br-/Br2, utilizing a highly efficient CoS2/CoS@Graphite Felt (GF) electrode. Notably, the anodic nitrile generation can be synergistically coupled with the cathodic hydrogen evolution reaction (HER). Through meticulous optimization of reaction parameters, we achieve an impressive 98% selectivity for octanenitrile at a current density of 60 mA cm-2 with a remarkable faradaic efficiency (FE) of 87%. Furthermore, our approach demonstrates excellent versatility, as we successfully evaluate both aliphatic and aromatic primary amines, highlighting its promising potential for practical applications in the field.

Update on novel synthetic approaches towards the construction of carbazole nuclei: a review

The carbazole scaffold is a significant entity in organic compounds due to its variety of biological and synthetic applications. Traditionally, carbazole skeletons have been synthesized either via the Grabe-Ullman method, Clemo-Perkin method or Tauber method. With the passage of time, these methods have been modified and explored to accomplish the synthesis of target compounds. These methods include hydroarylations, C-H activations, annulations and cyclization reactions mediated by a variety of catalysts to construct carbazole-based compounds. This brief review article intends to provide recent updates on important methodological developments reported for the synthesis of carbazole nuclei covering 2019-2023.

Electrochemically Driven Nickel-Catalyzed Halogenation of Unsaturated Halide and Triflate Derivatives

A robust electrochemically driven nickel-catalyzed halogen exchange of unsaturated halides and triflates (Br to Cl, I to Cl, I to Br, and OTf to Cl) is reported. A combination of NiCl2  ⋅ glyme as the precatalyst, 2,2'-bipyridine as a ligand, NMP as the solvent, and electrochemistry allowed the generation of a nickel species that promotes reductive elimination of the desired product. This paired electrochemical halogenation is compatible with a range of unsaturated halides and triflates, including heterocycles, dihaloarenes, and alkenes with good functional-group tolerance. Joint experimental and theoretical mechanistic investigations highlighted three catalytic events: i) oxidative addition of the aryl halide to a Ni(0) species to deliver a Ni(II) intermediate; ii) halide metathesis at Ni(II); iii) electrochemical oxidation of Ni(II) to Ni(III) to enable the formation of the desired aryl halide upon reductive elimination. This methodology allows the replacement of heavy halogens (I or Br) or polar atoms (O) with the corresponding lighter and more lipophilic Cl group to block undesired reactivity or modify the properties of drug and agrochemical candidates.

Recent Trends in the Petasis Reaction: A Review of Novel Catalytic Synthetic Approaches with Applications of the Petasis Reaction

The Petasis reaction, also called the Petasis Borono-Mannich reaction, is a multicomponent reaction that couples a carbonyl derivative, an amine and boronic acids to yield substituted amines. The reaction proceeds efficiently in the presence or absence of a specific catalyst and solvent. By employing this reaction, a diverse range of chiral derivatives can easily be obtained, including α-amino acids. A broad substrate scope, high yields, distinct functional group tolerance and the availability of diverse catalytic systems constitute key features of this reaction. In this review article, attention has been drawn toward the recently reported methodologies for executing the Petasis reaction to produce structurally simple to complex aryl/allyl amino scaffolds.

Direct synthesis of haloaromatics from nitroarenes via a sequential one-pot Mo-catalyzed reduction/Sandmeyer reaction

Herein, we report the direct synthesis of a wide variety of functionalized aromatic bromides, chlorides, iodides, and fluorides from nitroarenes in a sequential one-pot operation. This protocol is based on an air- and moisture-tolerant dioxomolybdenum-catalyzed reduction of nitroaromatics, employing pinacol as a reducing agent, which enables subsequent diazotization and halogenation steps. This methodology represents a step-economical, practical, and alternative procedure for synthesizing haloaromatics directly from nitroaromatics.

Recent advances in electrochemical functionalization using diazonium salts

Arenediazonium salts have gained attention in the scientific community due to their numerous synthetic applications. In the traditional method of dediazoniation of arenediazonium salts, the requirements for toxic oxidants and costly catalysts affect their cost-effectiveness and sustainability. However, recent advances in synthetic organic electrochemistry allow for the in situ reduction of arenediazonium salts, affording different functionalizations under mild reaction conditions and with a shorter reaction time. Herein, we report advances up to now of facile organic electrochemical syntheses using arenediazonium salt precursors that avoid the use of hazardous reductants.

Copper(I)-Mediated Divergent Synthesis of Pyrroquinone Derivatives and 2-Halo-3-amino-1,4-quinones

A divergent transformation of 2-amino-1,4-quinones for the synthesis of pyrroquinone derivatives and 2-halo-3-amino-1,4-quinones was disclosed. The mechanistic study showed that both the tandem cyclization and halogenation involved a Cu(I)-catalyzed oxidative radical process. This protocol not only constructed a series of novel pyrroquinone derivatives with high atom economy but also provided a new method of halogenation via directed C(sp²)-H functionalization with CuX (X = I, Br, Cl) serving as the X (X = I, Br, Cl) source.

An enzyme-mimic single Fe-N3 atom catalyst for the oxidative synthesis of nitriles via C─C bond cleavage strategy

The cleavage and functionalization of recalcitrant carbon─carbon bonds is highly challenging but represents a very powerful tool for value-added transformation of feedstock chemicals. Here, an enzyme-mimic iron single-atom catalyst (SAC) bearing iron (III) nitride (FeN₃) motifs was prepared and found to be robust for cleavage and cyanation of carbon-carbon bonds in secondary alcohols and ketones. High nitrile yields are obtained with a wide variety of functional groups. The prepared FeN₃-SAC exhibits high enzyme-like activity and is capable of generating a dioxygen-to-superoxide radical at room temperature, while the commonly reported FeN₄-SAC bearing FeN₄ motifs was inactive. Density functional theory (DFT) calculation reveals that the activation energy of dioxygen activation and the activation energy of the rate-determining step of nitrile formation are lower over FeN₃-SAC than FeN₄-SAC. In addition, DFT calculation also explains the catalyst's high selectivity for nitriles.

Homology Modeling, Molecular Docking, Molecular Dynamic Simulation, and Drug-Likeness of the Modified Alpha-Mangostin against the β-Tubulin Protein of Acanthamoeba Keratitis

Acanthamoeba species are capable of causing amoebic keratitis (AK). As a monotherapy, alpha-mangostin is effective for the treatment of AK; however, its bioavailability is quite poor. Moreover, the efficacy of therapy is contingent on the parasite and virulent strains. To improve readiness against AK, it is necessary to find other derivatives with accurate target identification. Beta-tubulin (BT) has been used as a target for anti-Acanthamoeba (A. keratitis). In this work, therefore, a model of the BT protein of A. keratitis was constructed by homology modeling utilizing the amino acid sequence from NCBI (GenBank: JQ417907.1). Ramachandran Plot was responsible for validating the protein PDB. The verified BT PDB was used for docking with the specified ligand. Based on an improved docking score compared to alpha-mangostin (AM), two modified compounds were identified: 1,6-dihydroxy-7-methoxy-2,8-bis(3-methylbut-2-en-1-yl)-9H-xanthen-9-one (C1) and 1,6-dihydroxy-2,8-bis(3-methylbut-2-en-1-yl)-9H-xanthen-9-one (C2). In addition, molecular dynamics simulations were conducted to analyze the interaction characteristics of the two bound BT–new compound complexes. During simulations, the TRP9, ARG50, VAL52, and GLN122 residues of BT-C1 that align to the identical residues in BT-AM generate consistent hydrogen bond interactions with 0–3 and 0–2. However, the BT-C2 complex has a different binding site, TYR 258, ILE 281, and SER 302, and can form more hydrogen bonds in the range 0–4. Therefore, this study reveals that C1 and C2 inhibit BT as an additive or synergistic effect; however, further in vitro and in vivo studies are needed.

Unusual Reactivities of ortho-Hydroxy-β-nitrostyrene

Nitrostyrene derivatives are widely used in organic syntheses as a substrate for Michael addition, photoisomerization and cycloaddition. In contrast, ortho-hydroxy derivatives exhibit unusual behaviors in these reactions. Conjugate addition proceeded upon treatment of the ortho-hydroxy-β-nitrostyrene with an amine; however, subsequent C–C bond cleavage readily occurred to afford the corresponding imine. Moreover, conversion of the trans-isomer to a cis-isomer did not occur efficiently, even when UV light was irradiated. We studied these unusual behaviors of β-nitrostyrene, focusing on the role of the ortho-hydroxy group.

Copper-Promoted One-Pot Sandmeyer-Type Reaction for the Synthesis of N-Aryltriazoles

Herein, we report the copper-catalyzed one-pot Sandmeyer-type reaction of aromatic amines with triazoles to afford N-aryl-1,2,3-triazoles. Diazonium salts, formed from aromatic amines and tert-butyl nitrite in the presence of fluoroboric acid, reacted with triazoles in a copper-catalyzed Sandmeyer-type reaction. The reaction proceeded under mild conditions to afford N-aryltriazoles in moderate to good yields. This method is amenable to a wide range of aromatic amines and triazoles and shows diverse functional group tolerance. Inhibition of the reaction upon the addition of free radical scavengers suggested a radical pathway, in which the aryl radical, copper, and triazole formed a complex that underwent reductive elimination to give aryltriazole compounds; this is consistent with the mechanism underlying the Sandmeyer reaction. Thus, we demonstrate a new effective strategy for the construction of C-N bonds via Sandmeyer-type reactions and a valuable alternative approach for the synthesis of aryltriazole derivatives.

Mild, Organo-Catalysed Borono-Deamination as a Key to Late-Stage Pharmaceutical Precursors and 18F-Labelled Radiotracers

A tris(pentafluorophenyl)borane catalysed method for the synthesis of boronic acid esters from aromatic amines in yields of up to 93% was devised. Mild conditions, benign reagents, short reaction times, low temperatures and a wide substrate scope characterize the method. The reaction was found applicable to the synthesis of boronic acid ester derivatives of complex drug molecules in up to 86% isolated yield and high purity suitable for labelling. These boronates were subsequently labelled with [¹⁸F]fluoride ion in radiochemical yields of up to 55% with and even without isolation of the boronate-intermediate.

Cyanomethylation of the Benzene Rings and Pyridine Rings via Direct Oxidative Cross-Dehydrogenative Coupling with Acetonitrile

A novel and efficient approach for the amine-directed dehydrogenative C(sp²)-C(sp³) coupling of arylamines with acetonitrile was reported by using FeCl₂ as the catalyst. Substituted anilines, aminopyridines, naphthylamines, and some nitrogen-containing heterocyclic arylamines react with inactive acetonitrile to form the corresponding arylacetonitriles in moderate to good yields. This protocol features nontoxic iron catalysis, efficient atom economy, nonprefunctionalized starting materials, good regioselectivity, and excellent compatibility of functional groups and aromatic rings, providing a novel, straightforward, and green approach toward arylacetonitriles.