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Background: The synthesis and biological evaluation of 1,4-naphthoquinone derivatives are of great interest since these compounds exhibit strong antibacterial, antifungal, antimalarial, and anticancer activities. The electronic properties of naphthoquinones are usually modulated by attaching functional groups containing nitrogen, oxygen, and sulfur atoms, which tune their biological potency and selectivity. Methods: A series of 13 amino acid 1,4-naphthoquinone derivatives was synthesized under assisted microwave and ultrasound conditions. The antibacterial activity of compounds was tested against American Type Culture Collection (ATCC): Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis, as well as 2 multidrug resistant pathogens: E. coli and S. aureus from clinical isolated. Minimal inhibitory concentration (MIC) was determined using the broth microdilution method. Results: MIC of derivatives 4–11, 14, and 16 showed antimicrobial activity against Gram-positive and Gram-negative bacteria. Antimicrobial activities of the compounds 4–8 and 14 were ≤MIC 24.7 μg mL−1 against all the reference strains; even more, compound 6 showed the most potent activity with an MIC of 3.9 μg mL−1 on S. aureus. On the clinical isolated, the compounds 7, 8, and 14 showed an MIC of 49.7 and 24.7 μg mL−1 against S. aureus and E. coli, respectively. About ADME properties and Osiris analysis, the compounds 4–16 presented high gastrointestinal absorption and good characteristics for oral bioavailability, and compound 14 was the less toxic. Conclusion: Amino acid 1,4-naphthoquinone derivatives showed good in vitro antibacterial activity against clinical strains, and modifications on C-3 with a chloride atom enhanced the efficiency against the same pathogens.

The hydantoin moiety is found in several bioactive compounds with important pharmacological properties such as antimicrobial, antifungal, anti-androgens, anticancer and the historical action anticonvulsant. Because of these reasons, the synthesis of these compounds and their derivatives is important to review considering the philosophy of the green chemistry. In this review, we present the actual importance in the green synthesis of hydantoins and their derivatives using green methods, such as microwave and ultrasound irradiation, ionic liquids, solid-phase and solvent-free synthesis. Finally, several green protocols reported have been discussed.

Struthanthus quercicola, a hemiparasitic plant known as “seca palo,” is used by Nahuatl traditional healers against diabetes, wounds, and rashes. We aimed to investigate the effects of different S. quercicola extracts, which were selected based on their traditional use in Tamazunchale, San Luis Potosí, on the cell viability and antioxidant activity in HeLa cell cultures. S. quercicola growing on Guazuma ulmifolia and Citrus sp. hosts was collected, and methanolic and ethanolic extracts as well as decoctions, infusions, and microwave-assisted extracts were obtained. The terpenoid, alkaloid, flavonoid, saponin, and tannin contents of each extract were evaluated qualitatively and quantitatively. The effects of different extracts on the viability of cervical adenocarcinoma (HeLa) cells were tested using an MTT assay. The differences in the total flavonoid and phenolic contents and free-radical scavenging activity in relation to the host and the extract were also determined. In assessments of the effects of the extracts on cell viability, eight organic extracts (4 from G. quercicola grown on Host 1 and 4 from G. quercicola grown on Host 2) were shown to decrease cell viability significantly in comparison with the control. However, the extract obtained by percolation (PMeOH) caused a significant increase in cell viability (p

In December 2019 the new coronavirus, severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), was discovered in Wuhan, China. Since then, its infectious disease (coronavirus infectious disease-19, COVID-19) has spread widely with more than 100 million confirmed cases and 2 million confirmed deaths as of February 6, 2021, with cases in 219 countries, areas, or territories. On January 30, 2020 the World Health Organization (WHO) declared the outbreak to be a public health emergency of international concern (WHO, 2020). Since then, researchers around the world have been working in developing vaccines and antiviral medicines. Despite this the actual pandemic situation needs an alternative and secure measure, and traditional medicine could be an answer. Medicinal plants and isolated compounds are promising therapies against the novel coronavirus SARS-CoV-2 to treat and control COVID-19. Up until now a few percentages of approved drugs are unaltered natural products or botanical drugs. Plants contain phytochemicals with antioxidant, antiinflammatory, and immunomodulatory properties. Consequently, a combination of active natural products with approved antiviral drugs could be an alternative to improve the biological effect and/or produce a synergistic effect as supportive agents to minimize clinical symptoms.

1,4−naftoquinone (NQ) molecules have been extensively evaluated as potent antibacterial compounds; however, their use is limited, since they have low water solubility and exhibit toxicities in healthy eukaryotic cells. A possible path to overcoming these challenges is the use of particulate vehicles, such as SBA-15, which is a biocompatible and biodegradable mesoporous silica material, that may enhance drug delivery and decrease dosages. In this work, an isotherm model-based adsorption of three NQs into SBA-15 microparticles was evaluated. Interactions between NQs and SBA-15 microparticles were modeled at the B3LYP/6-31+G(d,p) level of theory to understand the nature of such interactions. The results demonstrated that the adsorption of NQ, 2NQ, and 5NQ into SBA-15 fit the Freundlich adsorption model. According to theorical studies, physisorption is mediated by hydrogen bonds, while the most stable interactions occur between the carbonyl group of NQ and silica surfaces. Both experimental and theoretical results contribute to a deeper understanding of the use of SBA-15 or similar particles as nanovehicles in such a way that NQs can be modified in carbonyl or C3 to enhance adsorptions. The theoretical and experimental results were in accordance and contribute to a deeper understanding of how interactions between NQ-type molecules and SiO2 materials occur.

Background:Molecular organic photochemistry is concerned with the description of physical and chemical processes generated upon the absorption of photons by organic molecules. Recently, it has become an important part of many areas of science: chemistry, biology, biochemistry, medicine, biophysics, material science, analytical chemistry, among others. Many synthetic chemists are using photochemical reactions in crystals to generate different types of organic compounds since this methodology represents a green chemistry approach.Objective & Method:Chemical reactions in crystals are quite different from reactions in solution. The range of organic solid state reactions and the degree of control which could be achieved under these conditions are quite wider and subtle. Therefore, for a large number of molecular crystals, the photochemical outcome is not the expected product based on topochemical principles. To explain these experimental results, several physicochemical factors in crystal structure have been proposed such as defects, reaction cavity, dynamic preformation or photoinduced lattice instability and steric compression control. In addition, several crystal engineering strategies have been developed to bring molecules into adequate orientations with reactive groups in good proximity to synthesize complex molecules that in many cases are not available by conventional methods. Some strategies involve structural modifications like intramolecular substitution with different functional groups to modify intermolecular interactions. Other strategies involve chemical techniques such as mixed crystal formation, charge transfer complexes, ionic and organometallic interactions. Furthermore, some examples of the single crystal to single crystal transformations have also been developed showing an elegant method to achieve regio and stereoselectivity in a photochemical reaction.Conclusion:The several examples given in this review paper have shown the wide scope of photochemical reactions in organic molecular crystals. There are several advantages of carrying photochemical reaction in the solid state. Production of materials unobtainable by the traditional solution phase reactions, improved specificity, reduction of impurities, and enhancement in the yields by the reduction of side reactions. These advantages and the multidisciplinary nature of solid-state photochemistry make this discipline quite likely to develop a lot in the future.

In this work, the synthesis of thiohydantoins from l-amino acids and isothiocyanates was studied, using a high purity method based on the Edman cycle. This process, expected to occur through the Michael addition to a series of 1,4-naphthoquinone derivatives did not lead to the expected final product, rather leading to a colored mixture of compounds, where EPR spectra showed that some of them presented unpaired electrons, indicating that an electron transfer pathway was also involved in the reaction mixture. Detected organic radicals proved to be stable albeit with the use of different experimental conditions. Voltammetric results indicated that the reactions led to the formation of electroactive species, probably derived by homogeneous electron transfer between the reactive quinone moieties and the oxidizable urea functions within the hydantoin species.

A new synthetic strategy to obtain new linked 1,5-disubstituted tetrazole-1,2,3-triazoles via the Ugi-azide reaction followed by a copper-catalyzed alkyne-azide reaction (CuAAC) was developed. This strategy used solvent-free conditions for the Ugi-azide reaction. This two-step strategy affords the products in moderate to good yields. To the best of our knowledge, this is the first report using the CuAAC reaction as a post-condensation process in an Ugi-azide reaction and therefore, the first describing the synthesis of 1,5-disubstituted tetrazole (1,5-DS-T) linked to the 1,2,3-triazole moiety, which are molecules that may have potential applications in medicinal chemistry.

Polyoxometalates arise as significant catalysts in the field of organic chemistry due to their diverse properties and functions. Recent progress based on experimental evidence and density functional theory (DFT) calculations provides valuable information to demystify the chemistry of decatungstate anion, W10O32 4−. Particularly, functionalization of aldehydes by homolytic C–H bond cleavage can be efficiently achieved when it is catalyzed by this polyoxometalate. Two reaction mechanisms have been formulated to account for the role of W10O32 4− in organic chemical reactions: the single electron transfer and the hydrogen atom transfer (HAT) mechanisms. In this contribution, the HAT pathway for the acylation of dimethyl maleate is experimentally and quantum-chemically explored in detail. Results based on DFT calculations under the unrestricted formalism suggest that the acylation occurs in a barrierless process upon the formation of the lowest-in-energy triplet excited state of W10O32 4−. These outcomes agree well with the experimental evidence since the acylated adduct was produced at a 90% yield; in this regard, side reactions like radical couplings and decarbonylation resulted in less competitiveness. The current work may therefore help in the comprehension of the mechanistic details leading to the synthesis of organic compounds photocatalyzed by polyoxometalates, even under solar radiation.

Mannich bases are formed in a noncatalytic multicomponent reaction, which is promoted by ultrasound irradiation. The procedure avoids the use of toxic solvents, catalyst, and purification, generating the desired compounds in excellent yields and short reaction times.

Mannich bases are formed in a non-catalytic multicomponent reaction, which is promoted by ultrasound irradiation. The procedure avoid the use of toxic solvents, catalyst and purification, generating the desired compounds in excellent yields and short reaction times.

We performed an extensive analysis about the reaction conditions of the 1,4-Michael addition of amino acids to 1,4-naphthoquinone and substitution to 2,3-dichloronaphthoquinone, and a complete evaluation of stoichiometry, use of different bases, and the pH influence was performed. We were able to show that microwave-assisted synthesis is the best method for the synthesis of naphthoquinone&ndash, amino acid and chloride&ndash, naphthoquinone&ndash, amino acid derivatives with 79&ndash, 91% and 78&ndash, 91% yields, respectively. The cyclic voltammetry profiles showed that both series of naphthoquinone&ndash, amino acid derivatives mainly display one quasi-reversible redox reaction process. Interestingly, it was shown that naphthoquinone derivatives possess a selective antitumorigenic activity against cervix cancer cell lines and chloride&ndash, amino acid derivatives against breast cancer cell lines. Furthermore, the newly synthetized compounds with asparagine&ndash, naphthoquinones (3e and 4e) inhibited ~85% of SiHa cell proliferation. These results show promising compounds for specific cervical and breast cancer treatment.

The reaction of sodium azide with perfluorobenzene, containing an electron-withdrawing group, under microwave irradiation results in the fast preparation of p-substituted tetrafluorophenyl monoazides. Having an excess of sodium azide and a strong electron-withdrawing group like NO2 or CN, fluorophenyl diazides are also produced upon conventional or microwave heating. A synergic effect between the amount of sodium azide and the electron-withdrawing character of the substituents is observed giving different products. A discussion on the products and reaction mechanism is presented.

The nitrogen inversion of a N-phenyl aziridine fused to a succinimide ring is influenced by the presence of a phenyl ring in the succinimide moiety. The endo invertomer is favored, showing an unsymmetrical equilibrium in variable (1)H NMR studies.

The photoinduced and thermal denitrogenation of crystalline triazolines with bulky substituents leads to the quantitative formation of aziridines in clean solid-to-solid reactions despite very large structural changes in the transition from reactant to product. Analysis of the reaction progress by powder X-ray diffraction, solid-state (13)C CPMAS NMR, solid-state FTIR spectroscopy, and thermal analysis has revealed that solid-to-solid reactions proceed either through metastable phases susceptible to amorphization or by mechanisms that involve a reconstructive phase transition that culminates in the formation of the stable phase of the product. While the key for a solid-to-solid transformation is that the reaction occurs below the eutectic temperature of the reactant and product two-component system, experimental evidence suggests that those reactions will undergo a reconstructive phase transition when they take place above the glass transition temperature.

Background: Fluoroquinolones are widely prescribed synthetic antimicrobial agents. Quinolones act by converting their targets, gyrase and topoisomerase IV, into toxic enzymes that fragment the bacterial chromosome; the irreversible DNA damage eventually causes the killing of bacteria. Thorough knowledge of the structure-activity relationship of quinolones is essential for the development of new drugs with improved activity against resistant strains. Methods: The compounds were screened for their antibacterial activity against 4 representing strains using the Kirby-Bauer disk diffusion method. Minimal inhibitory concentration (MIC) was determined by measuring the diameter of the inhibition zone using concentrations between 250 and 0.004 μg/mL. Results: MIC of derivatives 2, 3, and 4 showed potent antimicrobial activity against gram-positive and gram-negative bacteria. The effective concentrations were 0.860 μg/mL or lower. MIC for compounds 5-11 were between 120 and 515 μg/mL against Escherichia coli and Staphylococcus aureus, and substituted hydrazinoquinolones 7-10 showed poor antibacterial activity against gram-positive and gram-negative bacteria compared with other quinolones. Conclusion: Compounds obtained by modifications on C-7 of norfloxacin with the acetylated piperazinyl, halogen atoms, and substituted hydrazinyl showed good in vitro activity - some even better than the original compound.

The solid-state photodenitrogenation of crystalline triazolines proceeds with high efficiency to form the corresponding aziridines in high chemical yields upon selection of the proper irradiation wavelength. It was shown that the solid-to-solid reactions occur by formation of the product in metastable crystalline phases.

Several benzofuroxans were obtained by photolysis of crystalline o -nitrophenylazides at ambient temperature. In this particular case, the solid matrix favored the elimination of nitrogen and exclusive formation of heterocyclic benzofuroxan. However, this reaction gives quantitative yields only with crystalline o -nitrophenylazides with a high melting point (above 50 °C).

The reaction of sodium azide with perfluorobenzene, containing an electron-withdrawing group, under microwave irradiation results in the fast preparation of p-substituted tetrafluorophenyl monoazides. Having an excess of sodium azide and a strong electron-withdrawing group like NO2 or CN, fluorophenyl diazides are also produced upon conventional or microwave heating. A synergic effect between the amount of sodium azide and the electron-withdrawing character of the substituents is observed giving different products. A discussion on the products and reaction mechanism is presented.

A novel reagent for photoaffinity labeling, 7-azido-1-ethyl-3-carboxylate-6,8-difluoroquinolone, was obtained by nucleophilic substitution of 1-ethyl-3-carboxylate-6,7,8-trifluoroquinolone. Photochemical reaction of this azide with diethyl amine gave 7-hydrazino-derivative as the major product. This compound was generated by singlet nitrene N–H insertion. In addition, 7-amino-1-ethyl-3-carboxylate-6,8-difluoroquinolone was also obtained.

Microwave-assisted pyrolysis of o-nitrophenyl azides gives benzofuroxans in good yields in short reaction times.

The reaction produces good yields only with crystalline o-nitrophenylazides (melting points above 50 °C).

The conversion of substrates (I) into 2-azido derivatives is followed by spontaneous N2 elimination to form the target compounds.

Microwave-assisted pyrolysis of o-nitrophenyl azides gives benzofuroxans in good yields in short reaction times.

Several pyridofuroxans were obtained by spontaneous N2 elimination from the corresponding 2-azido-3-nitropyridines. In this particular case, the presence of nitrogen in the pyridine ring must facilitate a cyclic extrusion mechanism. The pyridofuroxans prepared in this study did not present tautomerism as evidenced by NMR.