In this work, we conducted a study of 7-exo-trig cyclizations mechanism involving aryl, vinyl, and alkyl radicals on oxime ethers. Initially, the reaction of brominated oxime ether 9 a with (TMS)(3)SiH and AIBN gave rise to aryl radicals that underwent a 7-exo-trig cyclization on the oxime ether, yielding dibenzoxepine 10 a, and the ipso reaction and reduction products were obtained as well. Approximate rate constants at 80 degrees C for the 7-exo-trig (1.0x10(8) s(-1)) and the ipso cyclization (4.3x10(7) s(-1)) were determined by competition experiments. DFT calculations showed good agreement with the experimental results. The reduction rate constant of the N-alkoxyaminyl radical with (TMS)(3)SiH was calculated to be 4.1x10(-1) M-1 s(-1); while the rate constants for the 7-exo-trig cyclizations of vinyl and alkyl radicals on the oxime ether were estimated in the ranges of 10(6) s(-1)-10(8) s(-1) and 10(3) s(-1)-10(8) s(-1), respectively. The 7-exo-trig cyclization reactions involving aryl, vinyl, and alkyl radicals with oxime ethers were found to be an exothermic and irreversible process, with the oximic carbon showing a preference for nucleophilic alkyl radicals. This kinetic study contributes to the deeper understanding of radical-mediated cyclizations, enabling the efficient design of complex synthetic routes.

The presence of antibiotics in the environment has raised concerns due to their potential negative effects on ecosystems. Conventional water treatment methods are ineffective at removing antibiotics. This study aims to investigate the efficiency of Fenton-like processes catalyzed by delaminated clay and layered double hydroxides impregnated with Fe or Cu for the degradation of amoxicillin. The catalysts were obtained by synthesizing delaminated clay and layered double hydroxides and subsequently impregnating them with Fe or Cu. The characterization of catalysts involved X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). Catalytic activity was assessed by varying the concentration of hydrogen peroxide, the initial concentration of amoxicillin, and the amount of catalyst. The determination of byproducts was done by high-performance liquid chromatography (HPLC) with a quadrupole time-of-flight mass spectrometer (QqTof). The study found that layered double hydroxides impregnated with Fe or Cu were able to remove 100% of amoxicillin in just 20 min. The study identified 16 byproducts, indicating a degradation process. Under all of the studied conditions, the copper catalysts showed the highest percentage of amoxicillin removal.

In this research the sequential generation and cyclization of N-alkoxyaminyl radicals to produce 1-azaspiro[4.4]nonane, a prominent scaffold in organic and medicinal chemistry, was studied. Competition experiments in benzene at 80 °C with brominated oxime ethers using Bu3SnH as chain transfer and AIBN as the initiator generated vinyl or aryl radicals which were captured by oxime ethers, allowing approximate 5-exo-trig cyclization constants at 4.6 × 108 s-1 and 9.9 × 108 s-1 respectively to be established. Similar results were obtained by kinetic studies using the transition state theory (TST) from ab initio calculations with density functional theory (DFT) using the M06-2X, B3LYP, mPW1PW91 and TPSSh functionals in combination with the 6-311+G(d, p) basis set. Additionally, it was found that the 5-exo-trig cyclization of the N-alkoxyaminyl radical onto CC double bonds is a reversible process whose constants were determined to be in the range of 6.2 × 100 s-1 and 3.5 × 106 s-1 at 80 °C, depending on the nature of the substituents. The calculation of the radical stabilization energy (RSE) shows that the N-alkoxyaminyl radical is a very stable species and its reactivity in the addition on alkenes is governed by its nucleophilic character and the stability of the carbon-centered radical formed after cyclization. The reduction constant of the N-alkoxyaminyl radical with Bu3SnH in the gas phase at 80 °C was also estimated to be 3.4 × 100 M-1 s-1 through computational calculations. This information facilitates the rational planning of cascades and other methodologies applied to the construction of carbocyclic and aza-heterocyclic compounds.

The modified tannin by Mannich reaction was investigated for wastewater treatment. The removal of heavy metals, such as copper, chromium and mercury, in industrial wastewater was evaluated through the coagulation–flocculation technique, using modified Acacia tannin (MAT) as a coagulant agent. The successful tannin modification was evaluated by infrared spectopometry (FTIR), nuclear magnetic resonance (NMR); monitoring the removal of heavy metals was performed by atomic absorption (AA) and a direct mercury analyzer (DMA). Additionally, the parameters of water quality, total suspended solids (TSS), turbidity and chemical oxygen demand (COD) were assessed. Different doses of MAT were evaluated (375 ppm, 750 ppm, 1250 ppm and 1625 ppm) and three different levels of pH (4, 7 and 10). The highest percentages of removal obtained were copper 60%, chromium 87%, mercury 50%–80%, COD 88%, TSS 86% and turbidity 94%, which were achieved with the dose of 375 ppm of MAT at pH 10. The coagulation–flocculation process with the modified Acacia tannin is efficient for the removal of conventional parameters and for a significant removal of the metals studied.

Parkinson's disease (PD) is a neurodegenerative pathology characterized by resting tremor, rigidity, bradykinesia, and loss of dopamine-producing neurons in the pars compacta of the substantia nigra in the central nervous system (CNS) that result in dopamine depletion in the striatum. Oxidative stress has been documented as a key pathological mechanism for PD. Epidemiological studies have shown that smokers have a lower incidence of PD. In this aspect, different studies have shown that nicotine, a chemical compound found in cigarette, is capable of exerting beneficial effects in PD patients, but it can hardly be used as a therapeutic agent because of its inherent toxicity. Several studies have suggested that the use of nicotine analogs can have the same benefits as nicotine but lack its toxicity. In this study, we assessed the effects of two nicotine analogs, (E)-nicotinaldehyde O-cinnamyloxime and 3-(pyridin-3-yl)-3a,4,5,6,7,7a-hexahidrobenzo[d]isoxazole, in an in vitro model of PD. Initially, we performed a computational prediction of the molecular interactions between the nicotine analogs with the α7 nicotinic acetylcholine receptor (nAChR). Furthermore, we evaluated the effect of nicotine, nicotine analogs and rotenone on cell viability and reactive oxygen species (ROS) production in the SH-SY5Y neuronal cell line to validate possible protective effects. We observed that pre-treatment with nicotine or (E)-nicotinaldehyde O-cinnamyloxime (10 μM) improved cell viability and diminished ROS production in SH-SY5Y cells insulted with rotenone. These findings suggest that nicotine analogs have a potential protective effect against oxidative damage in brain pathologies.

A photocatalyzed redox generation of radicals from O-ethyl xanthates to generate electrophilic radicals under photoredox catalysis, using Ir(ppy)3 and blue LEDs irradiation is described. The protocol can be used in classical xanthate-based inter- and intra-molecular group transfer reactions and oxidative radical addition to several heteroaromatic systems. The process does not require high temperature and reactions are cleaner compared with the traditional peroxide initiation. In the oxidative addition to aromatic systems, the oxidation process is part of the catalytic cycle and does not require a stoichiometric oxidant such as DLP which is particularly difficult to separate from the product.

Herein we report the synthesis of a series of O-alkyl oximes of flavone and 6-hydroxyflavone using a simple experimental protocol under solvent free conditions with yields up to 87%. Cytotoxicity of all compounds was evaluated against MDA-MB-231, PC-3, A-549 and MRC-5 cells. IC50 values for two compounds were determined to be in the range 28.7-47.8 mu M against all tested cell lines. Oxime ethers derivatives showed IC50 values between 28.7 and 49.5 mu M against MDA-MB-231, while the best activity was obtained for 6-hydroxyflavone with an IC50 of 3.4 mu M against this cell line. Compounds containing the substituent hydroxyl at the position six of flavone system displayed the best antiproliferative activity over MDA-MB-231 cells, being necessary this group to improve the sensibility on this type of cells. The antiproliferative activity of 6-hydroxyflavone is drastically diminished when the carbonyl group of flavone is changed by an oxime ether.

The colonization of an exotic species by native herbivores is more likely to occur if that herbivore is a generalist. There is little information on the life-history mechanisms used by native generalist insects to colonize exotic hosts and how these mechanisms are affected by host properties. We examined the ability of the generalist seed beetle Stator limbatus Horn to colonize an exotic species. We compared its host preference, acceptability, performance, and egg size when ovipositing and developing on two native (Pithecellobium dulce (Roxb.) Benth and Senegalia riparia (Kunth)) and one exotic legume species (Leucaena leucocephala (Lam.)). We also analyzed the seed chemistry. We found that females recognize the exotic species as an unfavorable host for larval development and that they delayed oviposition and laid fewer and larger eggs on the exotic species than on the native species. Survivorship on the exotic host was 0%. Additionally, seeds of the native species contain five chemical compounds that are absent in the exotic species, and the exotic species contains three sterols, which are absent in the native legumes. Genetically based differences between beetles adapted to different hosts, plastic responses toward new hosts, and chemical differences among seeds are important in host colonization and recognition of the exotic host. In conclusion, the generalist nature of S. limbatus does not influence its ability to colonize L. leucocephala. Explanations for the colonization of exotic hosts by generalist native species and for the success of invasive species must be complemented with studies measuring local adaptation and plasticity.

A new and efficient two-step procedure for the preparation of 5,7-disubstituted 5,7-dihydropyrido[2,3-b:6,5-b′]diindoles, containing aryl-, benzyl- as well as alkyl-substituents has been developed. This methodology consists of a chemo-selective double Suzuki-Miyaura cross-coupling reaction followed by a fourfold Buchwald-Hartwig amination reaction. UV/VIS absorption and fluorescence measurements have been carried out for a selected series of compounds. The results are summarized and compared with those of the isomeric 5,7-disubstituted 5-7-dihydropyrido[3,2-b:5,6-b′]diindoles.

4-(Alkoxyamino)chroman-2-ones were synthesized via a 6- exo - trig cyclization of alkyl radicals obtained from α-bromoesters containing an oxime ether group. In the case of secondary bromides, the best results were achieved using tris(trimethylsilyl)silane as the chain transfer agent and Et3B as the initiator in dichloromethane at room temperature; the corresponding chromanones were produced in 58–70% yield. Low yields of the cyclized compounds were obtained in the case of tertiary alkyl bromides (20–25%). Products of premature reduction of carbon-centered radicals and addition of ethyl radicals to C=N bond were also observed.

The synthesis of the title chromanones leads to reasonably good yields and diastereoselectivity, when precursors contain a secondary alkyl bromide.

The asymmetric unit of the title compound, C16H13N3O2, contains two independent molecules in which the pyridine and benzene rings form dihedral angles of 81.7 (2) and 79.8 (2)degrees, indicating the twist in the molecules. In the crystal, weak C-H center dot center dot center dot N interactions link molecules into chains along [100].

In the title mol-ecule, C(19)H(21)BrN(2)O, the piperidone ring adopts a chair conformation with a total puckering amplitude Q(T) of 0.554 (2) Å. The dihedral angle between the benzene rings is 64.10 (7)°. There are no significant inter-molecular inter-actions.

Synthesis and in vitro assessment of antifungal activity of oximes, oxime ethers and isoxazoles. Objective. To synthesize and carryout a preliminary evaluation of the in vitro antifungal activity of oximes, oxime ethers and isoxazoles. Materials and methods. Oximeswere synthesized from aldehydes or ketones with NH2OH.HCl and K2CO3. Oxime ethers were prepared by alkylation of oximes withpropargyl bromide or 2-bromobenzyl bromide, using NaOH as base and acetone as solvent. The isoxazoles were obtained by 1,3-dipolarcycloadditions using ceric ammonium nitrate (CAN), chloramine T (CAT) and NaOCl. Products were identified or characterized usingnuclear magnetic resonance (NMR) and mass spectrometry (MS). Radial growth inhibition assays against Aspergillus niger and Fusariumroseum were carried out. Results. Five oximes, seven oxime ethers, four of them new, and four new isoxazoles were obtained. Theassessed substances exhibited antifungal activity in amounts of 1,5 mg and 3,0 mg. Conclusions. Although 1,3-dipolar cycloadditionsallowed to obtain the desired isoxazoles, this methodology produced a wide variety of side products that reduced yields and made difficultthe purification of the target products. Four of the tested compounds showed inhibition percentages greater than 80%.