Search Results (54)

Quinoline, a heterocyclic scaffold of paramount importance in medicinal and industrial chemistry, has garnered significant attention due to its versatile applications. Traditional synthetic methods, dating back over a century, have evolved into innovative strategies leveraging catalytic C–H bond activation, transition-metal-free protocols, and photo-induced oxidative cyclization. Recent advancements highlight the synergistic roles of catalysts, oxidants, and solvents in enhancing molecular reactivity and reaction efficiency. This review systematically summarizes state-of-the-art oxidative annulation techniques for quinoline synthesis, emphasizing mechanistic insights and practical applications. Full article

A series of porphyrinoids fused to highly electron-withdrawing bis(thiadiazolo)benzene units have been prepared and spectroscopically characterized. These structures have modified chromophores and exhibit large bathochromic shifts. The nickel(II), copper(II) and zinc complexes of a bis(thiadiazolo)benzoporphyrin were prepared, and these showed strong absorptions above 600 nm that shifted to longer wavelengths with increasing atomic number for the coordinated metal cations. Although the investigated porphyrinoids were poorly soluble, proton NMR data could be obtained, and these demonstrated that the structures possess global aromatic character. This was confirmed with nucleus-independent chemical shift (NICS) calculations and anisotropy of induced current density (AICD) plots. The AICD plots also demonstrate that the fused heterocyclic unit is disconnected from the porphyrinoid π-system, and in this respect, it differs from phenanthroline-fused porphyrinoids as it shows the presence of extended conjugation pathways. Full article

Heterocycles are widely present in natural products, pharmaceuticals, and organic functional materials. In heterocycle synthesis, Pd-catalyzed cascade C–H functionalization has been regarded as one of the most powerful approaches due to its advantages in terms of high atom efficiency and readily available starting materials. In this review, we will briefly introduce the major advances in palladium-catalyzed cascade C(sp³)–H activation and annulation for constructing different types of heterocycles through inter- and intramolecular pathways from 2010 to 2023. Full article

The synthetic approach based on a sequence of Buchwald–Hartwig cross-coupling and annulation through intramolecular oxidative cyclodehydrogenation has been used for the construction of novel 4-alkyl-4H-thieno[2′,3′:4,5]pyrrolo[2,3-b]quinoxaline derivatives. For the first time, these polycyclic compounds were evaluated for antimycobacterial activity, including extensively drug-resistant strains. A reasonable bacteriostatic effect against Mycobacterium tuberculosis H₃₇Rv was demonstrated. A plausible mechanism for antimycobacterial activity of heterocyclic analogues of indolo[2,3-b]quinoxalines has been advanced on the basis of their molecular docking data. Full article

The synthesis of pyrrolidine compounds with biological interest is an active research topic. Glycine could be a versatile starting material for making pyrrolidine derivatives. This review covers recent works on glycine-based [3+2] cycloaddition and combines other annulation reactions in the one-pot synthesis of pyrrolidine-containing heterocyclic compounds. Synthetic method development, substrate scope, and reaction mechanisms are discussed. Applications of the compounds in drug discovery are briefly mentioned. This paper is helpful for chemists in the development of efficient and sustainable methods for the preparation of bioactive pyrrolidine compounds. Full article

Coumarin and its annulated heterocycles are mainly found in natural products, many of which show significant biological activities and are used extensively for the preparation of pharmaceutical products. Investigation revealed that many heterocyclic compounds fused with coumarin moiety exhibited antihelmentic, hypnotic, insecticidal, antifungal, and anti-coagulant properties. In industry, coumarin scaffolds are widely used for the preparation of drugs, agrochemicals, pesticides, and dyes. In recent studies, several coumarin derivatives have been used in materials science for the preparation of organic cell imaging materials, fluorescent biological probes, etc. Due to their immense application potential in biological science and material chemistry, much attention has been paid by researchers towards the synthesis of a new class of coumarin annulated heterocycles. In this paper, the synthesis of coumarin-annulated polycyclic heterocycles via sequential Claisen rearrangement and tin-hydride mediated radical cyclization is reported. The requisite starting materials 3-((4-chlorobut-2-yn-1-yl)oxy)-2H-chromen-2-one (1) was prepared from 3-hydroxycoumarin and 1,4-dichlorobut-2-yne. The Claisen rearrangement of 1 in refluxing chlorobenzene afforded 1-(chloromethyl)pyrano[2,3-c]chromen-5(3H)-one (2). Finally, radical cyclization reactions were carried out smoothly using ⁿBu₃SnH and AIBN in toluene at 110 °C, leading to the coumarin-annulated polycyclic heterocycles in high yields. The process is operationally simple and easy to work-up, making it convenient for the preparation of coumarin annulated heterocycles. Full article

A novel synthesis strategy to access 2-alkoxyquinoline derivatives via a palladium-driven cascade reaction is disclosed. Unlike classic methods based on the alkylation of 2-quinolones with alkyl halides, the present method benefits from the de novo assembly of the quinoline core starting from 1,3-butadiynamides. Palladium-catalyzed reaction cascades with N-(2-iodophenyl)-N-tosyl-1,3-butadiynamides and primary alcohols as external nucleophiles proceed under mild reaction conditions and selectively deliver a variety of differently functionalized 4-alkenyl 2-alkoxyquinolines in a single batch transformation. Full article

Quinone imines are important derivatives of quinones with a wide range of applications in organic synthesis and the pharmaceutical industry. The attack of nucleophilic reagents on quinone imines tends to lead to aromatization of the quinone skeleton, resulting in both the high reactivity and the unique reactivity of quinone imines. The extreme value of quinone imines in the construction of nitrogen- or oxygen-containing heterocycles has attracted widespread attention, and remarkable advances have been reported recently. This review provides an overview of the application of quinone imines in the synthesis of cyclic compounds via the domino annulation reaction. Full article

The goal of this study was directed to synthesize a novel class of annulated compounds containing difuro[3,2-c:3′,2′-g]chromene. Friedländer condensation of o-aminoacetyl derivative 3 was performed with some active methylene ketones, namely, 1,3-cyclohexanediones, pyrazolones, 1,3-thiazolidinones and barbituric acids, furnished furochromenofuroquinolines (4,5), furochromenofuropyrazolopyridines (6–8), furochromenofurothiazolopyridines (9,10) and furochromenofuropyridopyrimidines (11, 12), respectively. Also, condensation of substrate 3 with 5-amine-3-methyl-1H-pyrazole and 6-amino-1,3-dimethyluracil, as cyclic enamines, resulted in polyfused systems 13 and 14, respectively. In vitro antimicrobial efficiency of the prepared heterocycles against microbial strains exhibited variable inhibition action, where compound 3 was the most effective against all kinds of microorganisms. A significant cytotoxic activity was seen upon the annulation of the starting compound with thiazolopyridine (9 and 10) as well as pyridopyrimidine moieties (11, 12 and 14). The spectroscopic and analytical results were used to infer the structures of the novel synthesized compounds. Full article

The construction of high-performance n-type semiconductors is crucial for the advancement of organic electronics. As an attractive n-type semiconductor, molecular systems based on perylene diimide derivatives (PDIs) have been extensively investigated over recent years. Owing to the fascinating aggregated structure and high performance, S-heterocyclic annulated PDIs (SPDIs) are receiving increasing attention. However, the relationship between the structure and the electrical properties of SPDIs has not been deeply revealed, restricting the progress of PDI-based organic electronics. Here, we developed two novel SPDIs with linear and dendronized substituents in the imide position, named linear SPDI and dendronized SPDI, respectively. A series of structural and property characterizations indicated that linear SPDI formed a long-range-ordered crystalline structure based on helical supramolecular columns, while dendronized SPDI, with longer alkyl side chains, formed a 3D-ordered crystalline structure at a low temperature, which transformed into a hexagonal columnar liquid crystal structure at a high temperature. Moreover, no significant charge carrier transport signal was examined for linear SPDI, while dendronized SPDI had a charge carrier mobility of 3.5 × 10⁻³ cm² V⁻¹ s⁻¹ and 2.1 × 10⁻³ cm² V⁻¹ s⁻¹ in the crystalline and liquid crystalline state, respectively. These findings highlight the importance of the structure–function relationship in PDIs, and also offer useful roadmaps for the design of high-performance organic electronics for down-to-earth applications. Full article

An attractive approach for the preparation of spirocyclic benzofuran–furocoumarins has been developed through iodine-catalyzed cascade annulation of 4-hydroxycoumarins with aurones. The reaction involves Michael addition, iodination, and intramolecular nucleophilic substitution in a one-step process, and offers an efficient method for easy access to a series of valuable spirocyclic benzofuran–furocoumarins in good yields (up to 99%) with excellent stereoselectivity. Moreover, this unprecedented protocol provides several advantages, including readily available materials, an environmentally benign catalyst, a broad substrate scope, and a simple procedure. Full article

Quinoline is a privileged heterocyclic ring which can be found in many drug molecules and bioactive compounds. The development of synthetic methods for making quinoline derivatives continuously attracts the interest of organic and medicinal chemists. This paper highlights 2-azidobenzaldehyde-based [4+2] annulation for the synthesis of quinoline derivatives including fused and spiro-quinolines, quinoline-4-ols, 4-aminoquinolines, and related compounds. Full article

Nowadays, organosulfur compounds provide new options in the development of full organic ion batteries. However, many drawbacks (such as kinetics limitations during the reversible oxidation of disulfides with cleavage of S–S bond, as well as solubility in non-aqueous electrolytes) make their commercialization difficult. Herein, a new concept for the design of organosulfur compounds with regulated redox properties and limited solubility is proposed. As a proof-of-concept, we designed peri-disulfo-substituted 1,8-naphthalimide derivatives, in which the alkyl chain length and halogen substituents (Cl or Br) at positions 3 and 6 are varied. The compounds were synthesized by an originally developed procedure starting from tetrahalonaphthalic anhydride via nucleophilic substitution at both peri-positions in the respective imide. Using ionic liquid electrolyte, it was found that the new peri-dithiolo-1,8-naphthalimides can participate in n- and p-type redox reactions at about 2.0 V and above 4.0 V vs. Li/Li⁺, respectively. The redox potentials are sensitive mainly to whether Cl or Br substituents are available in the molecule architecture, while the alkyl chain length determines the kinetics of the redox reactions. Among all compounds, the chloro-substituted compound with the shorter alkyl chain displays the best kinetics for both low- and high-voltage redox reactions. Full article

Substrate-controlled diversity-oriented synthesis of polycyclic frameworks via [4 + 2] and [3 + 2] annulations between ninhydrin-derived Morita–Baylis–Hillman (MBH) adducts and 3,4-dihydroisoquinolines under similar reaction conditions have been developed. The reaction provides diversity-oriented synthesis of a series of novel and structurally complex spiro multi heterocyclic skeletons in good yields (up to 87% and 90%, respectively) with excellent diastereoselectivities (up to >25:1 dr). In particular, the switchable [4 + 2] and [3 + 2] annulation reactions are controlled by tuning the hydroxyl protecting group on the ninhydrin-derived MBH adduct to deliver structural diverse spiro[indene-2,2′-[1,3]oxazino[2,3-a]isoquinoline] and spiro[indene-2,1′-pyrrolo[2,1-a]isoquinoline], respectively. Furthermore, the relative configuration and chemical structure of two kinds of cycloadducts were confirmed through X-ray diffraction analysis. Full article