Synthetic Protocol Research Articles

Cascade [3 + 2] Annulation of 1,3-Dicarbonyl Compounds and Ethyl Secondary Amines for Pyrrole Synthesis via Poly C(sp3)-H Bond Functionalization.

The synthesis of polyfunctionalized pyrroles via the cascade reactions of 1,3-dicarbonyl compounds and two molecules of ethyl secondary amines has been realized via simple iodine catalysis in the presence of Dess-Martin periodinane (DMP). The formation of the target pyrrole products involves the formation of one new C-C and two new C-N bonds via the major functionalization of six C(sp3)-H bonds, presenting a highly novel and efficient synthetic protocol toward pyrrole scaffolds.

Introduction of Phosphinine Ring into Aromatic Systems via Alkyne Cyclization

Recently developed synthetic protocols for the preparation of λ3‐phosphanaphthalenes have broadened the general scope of organophosphorus chemistry, but a versatile protocol is still missing. Here, we describe a scalable synthetic approach for the construction of various substituted phosphanaphthalenes. We have obtained 11 derivatives through rigorous study and have demonstrated the robustness of this method. The optical properties of these phosphorus compounds and their aza and carbo analogues have been experimentally compared. Here, we show the power of the method in extending the synthesis to even larger polycyclic aromatic systems with embedded phosphine rings toward its potential applicability to materials science.

Ansa–Ferrocene Derivatives as Potential Therapeutics

It has been known since the 1990s that the introduction of a ferrocenyl–type substituent into compounds with proven biological activity can improve their properties. More recently, it was also shown that a carbon bridge connecting the two cyclopentadienyl rings in ferrocene derivatives could enhance the biological properties of the new compounds compared to those without them. However, the synthesis of ferrocenes with this additional linker, known as ansa–ferrocenes, is more difficult due to advanced synthetic protocols and the phenomenon of planar chirality in ring–substituted compounds. As a result, research into the formation of hybrids, conjugates and other ansa–ferrocene derivatives has not been widely conducted. This review discusses the potential biological properties of these units, covering scientific articles published between 1980 and 2024.

First Example of Single‐Crystal Nanodiamonds Immobilized in Porous SiO2‐Aerogel Matrix: Synthesis and Characterization

AbstractA first composite material containing uniformly dispersed disaggregated detonation nanocrystalline diamonds (DNDs) in SiO2 aerogel matrix was prepared. The synthetic protocol included hydrolysis of tetramethyl orthosilicate (Si(OMe)4, TMOS) by hydrosol of surface carboxylated DNDs with a typical size of 4–5 nm with DMSO serving as a cosolvent and a stabilizer of DND single crystals. Composite samples containing DNDs in silica aerogel matrix in concentration 1.0, 0.1 and 0.01 % w/w were prepared at ambient temperature. HRTEM data revealed that DNDs nanocrystals were uniformly distributed in aerogel and did not form aggregates. Textural and optical composites’ properties were determined.

Ursolic Acid Conjugates: A New Frontier in Anticancer Drug Development.

New Ursolic Acid (UA) conjugates were synthesized using optimized synthetic protocols through the molecular hybridization approach at C-3 and C-28. This resulted in the targeted molecules being produced in good yields. Some of the synthesized conjugates showed significantly relevant bioactivity against mammalian cells and in animal models of cancers. Selected UA conjugates were tested against bladder and breast cancer cell lines. The conjugates showed moderate to significantly enhanced antiproliferative activities against Triple Negative Breast Cancer (TNBC; MDA-MB 231), which is an aggressive tumor making up about 10-15 % of all breast cancers and bladder (T24 and 5637) cancer cell lines. These properties were superior to the parent UA. Among all the synthesized compounds, 18 c and 18 d have exhibited promising antiproliferative and cytotoxic properties against all tested cancer cell lines. However, 18 d has proved to be exceptionally selective for cancer cell lines, showing more cytotoxicity towards them than normal epithelial cells (MCF-12A). Compound 18 d has demonstrated cytotoxicity against tumor cells, including those intrinsically resistant to chemotherapy drugs such as 2-difluoro-deoxy cytidine (Gemcitabine). The activity of the UA conjugates on tumor cells was mediated by multiple cytotoxic mechanisms, including drug-induced cytotoxic autophagy and programmed cell death, indicating a novel possibility of combination therapy.

Base-Mediated Annulation of ortho-Iminophenols and ortho-Vinylphenols with MBH Carbonates of Isatins: Straightforward Access to Dihydrobenzofuran and Benzofuran Derivatives.

We have developed a convenient synthetic protocol for efficient construction of significant dihydrobenzofuran and benzofuran scaffolds by Lewis base-mediated annulation reaction ortho-iminophenols and ortho-vinylphenols with MBH carbonates of isatins under mild and metal-free conditions. The selective generation of different kinds of dihydrobenzofuran and benzofuran derivatives was successfully achieved by employing different substituted isatin-derived MBH carbonates with ortho-N-tosyliminophenols and ortho-vinylphenols. The features included broad substrate scopes, excellent functional group compatibility, high molecular diversity, and atomic economy.

Ligand engineering towards electrocatalytic urea synthesis on a molecular catalyst

Electrocatalytic C-N coupling from carbon dioxide and nitrate provides a sustainable alternative to the conventional energy-intensive urea synthetic protocol, enabling wastes upgrading and value-added products synthesis. The design of efficient and stable electrocatalysts is vital to promote the development of electrocatalytic urea synthesis. In this work, copper phthalocyanine (CuPc) is adopted as a modeling catalyst toward urea synthesis owing to its accurate and adjustable active configurations. Combining experimental and theoretical studies, it can be observed that the intramolecular Cu-N coordination can be strengthened with optimization in electronic structure by amino substitution (CuPc-Amino) and the electrochemically induced demetallation is efficiently suppressed, serving as the origination of its excellent activity and stability. Compared to that of CuPc (the maximum urea yield rate of 39.9 ± 1.9 mmol h−1 g−1 with 67.4% of decay in 10 test cycles), a high rate of 103.1 ± 5.3 mmol h−1 g−1 and remarkable catalytic durability have been achieved on CuPc-Amino. Isotope-labelling operando electrochemical spectroscopy measurements are performed to disclose reaction mechanisms and validate the C-N coupling processes. This work proposes a unique scheme for the rational design of molecular electrocatalysts for urea synthesis.

A Rapid, Greener, and Sustainable Synthesis of N-Acylhydrazones of Isoniazid in a Deep-Eutectic Solvent

AbstractThis study introduces an efficient, environmentally friendly, and sustainable method for synthesizing N-acylhydrazone analogues by engaging isoniazid in a condensation reaction with variously substituted benzaldehydes. The deep-eutectic solvent (ZnCl2/urea) employed in this study acted not only as a solvent but also as a catalyst to facilitate the synthesis of the target compounds within two to six minutes without the requirement of any lengthy purification techniques. The synthetic protocol is operationally simple and offers other remarkable advantages such as a short reaction time, good to excellent yields, a scalable protocol, and a recyclable and reusable catalyst. Additionally, green metrics calculations suggest the present method to be environmentally benign. Finally, the frontier molecular orbitals and the global reactivity parameters of the synthesized compounds were predicted by using density functional theory calculations.

Plasmonic semi shells derived from simultaneous in situ gold growth and anisotropic acid etching of ZIF-8 for photothermal ablation of metastatic breast tumor

Open nanoshells such as nanobowls or nanocups collectively described as ‘semi shells’ have unique plasmonic properties due to their lack of symmetry. So far, their fabrication was based on multistep and laborious methods such as solid state sputter coating or selective deposition/etching using sacrificial templates. In this work, we report a rapid one step colloidal synthetic protocol for PEGylated semi-shell (SS) fabrication by simultaneous facet specific anisotropic chemical etching of rhombic dodecahedral ZIF-8 and heterogenous nucleation & growth of gold. The SS possesses a strong localized surface plasmon resonance in the near-infrared region, which is retained after surface passivation with polyethylene glycol and subsequent cryopreservation for extended shelf-life. Freshly reconstituted PEGylated SS was found to be safe & non-toxic in healthy C57BL/6 mice post intravenous administration. The PEGylated SS displayed significant photothermal efficiency of ~37% with 808 nm laser irradiation. Preclinical assessment of intra-tumoral photothermal efficacy indicated complete remission of primary breast tumor mass with insignificant metastasis to vital organs in 4T1 FL2 tumor bearing CD1 nude mice. Further, PEGylated SS mediated photothermal therapy also yielded morbidity free survivael of 75% for up to 90 days, indicating their potential to significantly improve outcomes in advanced breast tumors.

Highly Efficient Catalysis of Pyridinium p‐Toluenesulfonate (PPTS): Two Facile One‐Pot Protocols for the Synthesis of 2,3‐Disubstituted Quinazolinone Scaffolds

AbstractTwo different one‐pot synthetic protocols have been developed for obtaining 2,3‐disubstituted quinazolin‐4(3H)‐ones using pyridinium p‐toluenesulfonate (PPTS) as catalyst. The two‐component reaction involves isatoic anhydride and N‐acetyl amine whereas the three‐component reaction use isatoic anhydride, aryl amine and β‐diketone in Toluene under classical heating at 80–100 °C to afford 2,3‐disubstituted quinazolin‐4(3H)‐ones in good yields. The two‐component reactions are compatible with various substituted aryl/alkyl amines.

Electrochemical Construction of C−F Bonds: Recent Advances and Future Perspectives

AbstractIdeal pathways to synthesize fluorinated compounds were pursued for over 100 years, due to wide application of organofluorides in materials, agrochemicals and pharmaceuticals. In this regard, electro‐organic synthesis, evolved as a sustainable and scalable approach in various synthetic protocols, stands out as a promising strategy. As a result, many novel and attracting applications of introduction of fluorine items into organic compounds by direct and redox‐mediated electrochemical methods has been reported, especially in recent five years. In this review, we are aim to highlight the reaction scopes, reaction mechanism, the fundamental aspects and the fluorine source variation in electrochemcial fluoriation transformation.

Palladium-Catalyzed Double Decarboxylative [3 + 2] Annulation of Naphthalic Anhydrides with Internal Alkynes.

A palladium-catalyzed [3 + 2] annulation of naphthalic anhydrides with internal alkynes has been developed. The present protocol offers an efficient and convenient route to access a series of 1,2-disubstituted acenaphthylenes with excellent functional group compatibility. The reaction is proposed to proceed through a double decarboxylation sequence. The reported synthetic protocols can be extended to napthalene- and perylenedicarboximide-containing substrates. The molecular structures, photophysical properties, and frontier molecular orbitals of the obtained adducts were investigated by X-ray crystallography, UV-vis and fluorescence spectroscopy, and DFT calculations.

Rethinking Nanoparticle Synthesis: A Sustainable Approach vs. Traditional Methods.

This review portrays a comparison between green protocols and conventional nanoparticle (NP) synthesis strategies, highlighting each method's advantages and limitations. Various top-down and bottom-up methods in NP synthesis are described in detail. The green chemistry principles are emphasized for designing safe processes for nanomaterial synthesis. Among the green biogenic sources plant extracts, vitamins, enzymes, polysaccharides, fungi (Molds and mushrooms), bacteria, yeast, algae, and lichens are discussed. Limitations in the reproducibility of green protocols in terms of availability of raw material, variation in synthetic protocol, and selection of material due to geographical differences are elaborated. Finally, a conclusion is drawn utilizing green chemical principles, & a circular economy strategy to minimize waste generation, offering a promising framework for the synthesis of NPs emphasizing sustainability.

Identifying synthetic variables influencing the reproducible microfluidic synthesis of ZIF nano- and micro-particles

The reproducible synthesis of nano- and -micro particles is a critical step in multiple synthetic and industrial processes. Microfluidic synthesis offers numerous advantages for development of precise, reliable, and industrially useful synthesis protocols. However, the influence of different synthetic variables on reproducibility in microfluidic synthesis is underexplored. In this work, we systematically study the influence of key synthetic parameters on the microfluidic synthesis of four Zeolitic Imidazolate Frameworks (ZIFs): ZIF-7, ZIF-8, ZIF-9, and ZIF-67. Utilizing a coiled tube microfluidic setup, we explore the influence of key synthetic parameters such as reagent concentration, stoichiometry, aging time, and nine modulators (pH-altering agents, surfactants, and polar polymers). Most importantly, we evaluate the impact of these variables in combination with the role of mixing, using the Dean flow model. Lastly, we focus on the reproducibility problems that a coiled reactor presents at specific flowrates and how these problems can be recognized and avoided. Overall, the insights collected from this work inform the design of synthetic protocols and enhance material reproducibility and control in microfluidic nano- and micro-particle synthesis.

Synthetic Protocols, Structural Activity Relationship, and Biological Activity of Piperazine and its Derivatives.

The versatile basic structure of piperazine allows for the development and production of newer bioactive molecules that can be used to treat a wide range of diseases. Piperazine derivatives are unique and can easily be modified for the desired pharmacological activity. The two opposing nitrogen atoms in a six-membered piperazine ring offer a large polar surface area, relative structural rigidity, and more acceptors and donors of hydrogen bonds. These properties frequently result in greater water solubility, oral bioavailability, and ADME characteristics, as well as improved target affinity and specificity. Various synthetic protocols have been reported for piperazine and its derivatives. In this review, we focused on recently published synthetic protocols for the synthesis of the piperazine and its derivatives. The structure-activity relationship concerning different biological activities of various piperazine-containing drugs was also highlighted to provide a good understanding to researchers for future research on piperazines.

Brønsted Acidic Ionic Liquid: An Efficient Organocatalyst for the Synthesis of Pyrrolo[1,2-a]indoles under Neat Conditions

AbstractA new synthetic approach has emerged for constructing 9H-pyrrolo[1,2-a]indole scaffolds by the reactions between indoles and chalcones under metal- and solvent-free conditions at 80 °C. The reaction occurs smoothly in the presence of a Brønsted acidic ionic liquid, 1-methyl-3-(4-sulfobutyl)-1H-imidazol-3-ium tosylate, as a catalyst, permitting the synthesis of the desired products with satisfactory yields. The developed protocol is applicable to the construction of biologically important pyrrolo[1,2-a]indole derivatives from easily accessible chalcones having various substituents. The process commences with Michael addition to chalcones, followed by annulations induced by the elimination of a water molecule, yielding the 9H-pyrrolo[1,2-a]indole scaffolds. Several control experiments were carried out to achieve a better understanding of the reaction pathway. The feasibility of recycling the catalyst was also demonstrated. This method produces water as the sole byproduct and represents a green synthetic protocol. The clean reaction, easily accessible reactants, and the metal- and solvent-free and environmentally friendly reaction conditions are the notable advantages of this procedure.

Optimization of the Introduction of 2,6-Dimethylphenol at the C4-Atom of 2’-Deoxythymidine for the Preparation of Modified Oligonucleotides

Nucleic acids, including DNA and RNA, are vital for genetic information storage and expression, finding applications in diverse fields. Chemical synthesis is commonly used for nucleic acid modification, utilizing protecting groups to selectively modify specific positions without disrupting the overall structure. This study focuses on optimizing the introduction of a 2,6-dimethylphenoxy group at the C4 position of a protected 2’-deoxythymidine, a modification for enhancing stability, binding affinity, and expanding chemical diversity for future applications in therapeutics, diagnostics, and nanomaterials. Silylation was used as the initial step for 2’-deoxythymidine protection, followed by the preparation of the modified nucleoside. Optimization of synthetic procedures involved adjustments of reaction parameters, such as solvent and reagent stoichiometry, using small- and large-scale reactions. Extensive experimentation revealed that changing the solvent from tetrahydrofuran to dichloromethane and using 1,8-diazabicyclo [5.4.0] undec-7-ene as the base provided significant progress in reaction efficiency. Analytical techniques, including thin-layer chromatography and 1H Nuclear Magnetic Resonance spectroscopy, were employed for monitoring and confirmation of compound identity and purity. Successful optimization of the synthetic protocol will contribute to nucleic acid modification chemistry advancement with potential applications in therapeutics or diagnostics.

Novel spirooxindole-triazole derivatives: unveiling [3+2] cycloaddition reactivity through molecular electron density theory and investigating their potential cytotoxicity against HepG2 and MDA-MB-231 cell lines.

A novel analogue of hybrid spirooxindoles was synthesized employing a systematic multistep synthetic approach. The synthetic protocol was designed to obtain a series of spirooxindole derivatives incorporating triazolyl-s-triazine framework via [3 + 2] cycloaddition (32CA) reaction of azomethine ylide (AY) with the corresponding chalcones (6a-d). Unexpectedly, the reaction underwent an alternate route, leading to the cleavage of the s-triazine moiety and yielding a series of spirooxindole derivatives incorporating a triazole motif. A comprehensive investigation of the 32CA reaction mechanism was conducted using Molecular Electron Density Theory (MEDT). The viability of all compounds was evaluated through an MTT assay, and the IC50 values were determined using Prism Software. The antiproliferative efficacy of the synthesized chalcones and the corresponding spirooxindole derivatives was assessed against two cancer cell lines: MDA-MB-231 (triple-negative breast cancer) and HepG2 (human hepatoma). These findings were compared with Sorafenib, which was used as a positive control. The results revealed that chalcones (6c and 6d) were the most active among the tested chalcones, with IC50 values of 7.2 ± 0.56 and 7.5 ± 0.281µM for (6c) and of 11.1 ± 0.37 and 11.0 ± 0.282µM for (6d), against MDA-MB-231 and HepG2, respectively. Spirooxindoles (9b, 9c, 9h, and 9i) exhibited the highest activity with IC50 values ranging from 16.8 ± 0.37µM to 31.3 ± 0.86µM against MDA-MB-231 and 13.5 ± 0.92µM to 24.2 ± 0.21µM against HepG2. In particular, spirooxindole derivatives incorporating 2,4-dichlorophenyl moiety were the most active, with an IC50 of 16.8 ± 0.37µM for (9h) against MDA-MB-23 and 13.5 ± 0.92µM for (9i) against HepG2. Interestingly, the IC50 of compound (6c) (7.2µM) exhibited better activity than that of Sorafenib (positive control) (9.98µM) against MDA-MB-231. Molecular docking, ADMET, and molecular dynamic simulations were conducted for the promising candidates (6b, 6c, and 9h) to explore their binding affinity in the EGFR active site.

Synthesis and spectroscopic studies of triazole-based macroheterocycles containing eudesmane-type sesquiterpenoid moieties

Chiral recognition is one of the most important and fascinating areas in supramolecular chemistry. Chiral macrocycles, especially chiral macrocyclic hosts, having stable structures, adjustable internal cavities to encapsulate and complexation have been developed during the last decade. Attention has been paid on the synthesis of covalently linked of rigid units on the side chain of macrocycles with active binding motifs. In this study, new synthetic protocols has been developed for preparation of optically active triazole-based macrocyclic compounds in which eudesmane-type sesquiterpene lactones act as pendent moieties by the implementation of the copper(I)-catalyzed azid-alkyne cycloaddition strategies. The described protocols provided mild reaction conditions, high yields and high atom- and step-economy. New macrocycles with hanging dihydroisoalantolactone units, different combinations of heteroatoms, and ring sizes in the range of 16–36 atoms were characterized by NMR and UV–vis spectroscopy and mass spectrometry analysis. The molecular structures and intermolecular interactions of two new macrocyclic compounds were elucidated using single-crystal X-ray crystallography. Upon addition of Mg(II) or Zn(II) cations to these novel ligands, using titration experiments we observed the formation of 1:1 (16:Mg2+) complexes and 1:1 to 2:1 (16:Zn2+) complexes, respectively, according to stoichiometry. The result suggests that dihydriisoalantolactone and triazole units within the molecules formed complexes with Mg (II) and Zn (II) ions in solution.

Novel quinolin-4-ylcarbonylhydrazine having N-(3-arylacryloyl) moiety: Design, synthesis and biological evaluation as potential cytotoxic agents against MDA-MB-231 via tubulin assembly inhibition

A new set of quinolin-4-ylcarbonylhydrazine derivatives 7a-i and 9a,b bearing 3-arylacryloyl moiety has been synthesized and investigated for their potential anticancer activity. The synthetic protocol involves the following step: the target quinoline derivatives 7a-i and 9a,b appended to the acryloyl moiety were synthesized from quinolin-4-carbohydrazide intermediate with respective ethyl 2-arylamido-3-arylacrylate compounds. The cytotoxic activity study was evaluated using the functional MTT method. The most of target compounds displayed potent cytotoxic activity against MDA-MB-231 cell line. Among them, compounds 7d and 7 h were found to be promising antiproliferative agents with IC50 values of 4.04 and 1.78 μM, respectively, relative to the effective anticancer drug, Dox (IC50 = 5.33 μM). Compound 7 h exhibited cytotoxic activity by causing cell cycle to block at G2/M phase in addition to pro-apoptotic effect, as shown by flow cytometric measurement. In addition, the inhibitory action against β-tubulin polymerization was investigated. Finally, compound 7 h diminished the level of mitochondrial potential by almost 2.8-fold compared to control, indicating that the cellular death proceeds through the provoke of the intrinsic mitochondrial pathway of apoptosis.