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Geminal (gem-) disubstitution in heterocyclic monomers is an effective strategy to enhance polymer chemical recyclability by lowering their ceiling temperatures. However, the effects of specific substitution patterns on the monomer's reactivity and the resulting polymer's properties are largely unexplored. Here we show that, by systematically installing gem-dimethyl groups onto ϵ-caprolactam (monomer of nylonâ 6) from the α to ϵ positions, both the redesigned lactam monomer's reactivity and the resulting gem-nylonâ 6's properties are highly sensitive to the substitution position, with the monomers ranging from non-polymerizable to polymerizable and the gem-nylon properties ranging from inferior to far superior to the parent nylonâ 6. Remarkably, the nylonâ 6 with the gem-dimethyls substituted at the γ position is amorphous and optically transparent, with a higher Tg (by 30 °C), yield stress (by 1.5â MPa), ductility (by 3×), and lower depolymerization temperature (by 60 °C) than conventional nylonâ 6.
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Herein, we report a one-pot method for enantioselective C-H allylation of pyridines at C3 via tandem borane and palladium catalysis. This method involves borane-catalyzed pyridine hydroboration to generate dihydropyridines, then palladium-catalyzed enantioselective allylation of the dihydropyridines with allylic esters, and finally air oxidation of the allylated dihydropyridines to afford the products. This method enables the introduction of an allylic group at C3 with excellent regio- and enantioselectivities.
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Achieving C3-selective pyridine functionalization is a longstanding challenge in organic chemistry. The existing methods, including electrophilic aromatic substitution and C-H activation, often require harsh reaction conditions and excess pyridine and generate multiple regioisomers. Herein, we report a method for borane-catalyzed tandem reactions that result in exclusively C3-selective alkylation of pyridines. These tandem reactions consist of pyridine hydroboration, nucleophilic addition of the resulting dihydropyridine to an imine, an aldehyde, or a ketone, and subsequent oxidative aromatization. Because the pyridine is the limiting reactant and the reaction conditions are mild, this method constitutes a practical tool for late-stage functionalization of structurally complex pharmaceuticals bearing a pyridine moiety.
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Aldehídos , Boranos , Alquilación , Catálisis , Iminas , Cetonas , Estructura Molecular , PiridinasRESUMEN
We designed a borane/gold(I) co-catalytic system and used it for C-H functionalization reactions and cycloaddition reactions between tertiary amines and α-alkynylenones. Both reactions effectively incorporated a furan ring into the amine.
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Herein, we report that, by using chiral bicyclic bisborane catalysts, we have achieved the first highly regio-, diastereo-, and enantioselective direct asymmetric vinylogous Mannich reactions of acyclic α,ß-unsaturated ketones. The strong Lewis acidity and steric bulk of the bisborane catalysts were essential for the observed high yields and selectivities.
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Herein, we report a method for in situ generation of N-aryliminium ions via reactions of N,N-dimethylanilines with diiodomethane. We used the method to prepare tetrahydroquinolines via one-pot three-component reactions between N,N-dimethylanilines, diiodomethane, and olefins. This transformation involves initial reaction of the aniline with diiodomethane to form an iodomethylammonium salt, which undergoes fragmentation accompanied by elimination of methyl iodide to give an N-aryliminium ion, which is trapped by the olefin via [4 + 2] cycloaddition to give the final product. This method for generating N-aryliminium ions requires neither a catalyst nor a strong oxidant, suggesting that it can be expected to find broad utility, especially for substrates that are sensitive to Lewis acids, transition metals, or strong oxidants.
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Herein, we report that highly chemoselective and enantioselective reduction of 2-vinyl-substituted pyridines has been achieved for the first time. The reaction, which uses chiral spiro-bicyclic bisboranes as catalysts and HBpin and an acidic amide as reducing reagents, proceeds through a cascade process involving 1,4-hydroboration followed by transfer hydrogenation of a dihydropyridine intermediate. The retained double bond in the reduction products permits their conversion to natural products and other useful heterocyclic compounds by simple transformations.
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The present study was designed to examine whether Ramipril (an inhibitor of angiotensin-converting enzyme) affected spontaneous hypertension-induced injury of cerebral artery by regulating connexin 43 (Cx43) expression. Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) were randomly divided into WKY, WKY + Ramipril, SHR, and SHR + Ramipril groups (n = 8). The arterial pressure was monitored by the tail-cuff method, and vascular function in basilar arteries was examined by pressure myography. Hematoxylin-eosin (HE) staining was used to show vascular remodeling. The expression and distribution of Cx43 was determined by using immunofluorescence and immunohistochemistry analysis. The protein and mRNA levels of Cx43 were examined by Western blot and real-time PCR analysis, respectively. The results showed that chronic Ramipril treatment significantly attenuated blood pressure elevation (P < 0.01, n = 8) and blood vessel wall thickness in SHR (P < 0.01, n = 8). The cerebral artery contraction rate in the SHR group was higher than that in the WKY group (P < 0.05, n = 8). The cerebral artery contraction rate in the SHR + Ramipril group was lower than that in the SHR group (P < 0.05, n = 8). Pretreatment with 2-APB (Cx43 non-specific blocker) or Gap26 (Cx43 specific blocker) significantly decreased the vasoconstriction rate, while pretreatment with AAP10 (Cx43 non-specific agonist) significantly increased the vasoconstriction in the SHR + Ramipril group (P < 0.05, n = 8). In addition, the expression of Cx43 mRNA and protein in cerebral arteries of SHR group was higher than that of WKY group (P < 0.05, n = 8). The mRNA and protein expression of Cx43 in cerebral arteries of SHR + Ramipril group was significantly lower than that of SHR group (P < 0.05, n = 8). These results suggest that Ramipril can down-regulate the expression of Cx43 mRNA and protein in cerebral arterial cells of SHR, lower blood pressure, promote vasodilation, and improve arterial damage and vascular dysfunction caused by hypertension.
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Arterias Cerebrales/efectos de los fármacos , Conexina 43/metabolismo , Ramipril/farmacología , Remodelación Vascular , Animales , Presión Sanguínea , Arterias Cerebrales/metabolismo , Hipertensión/tratamiento farmacológico , Distribución Aleatoria , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKYRESUMEN
A new series of spiro-bicyclic bisborane catalysts has been prepared by means of hydroboration reactions of C2 -symmetric spiro-bicyclic dienes with HB(C6 F5 )2 and HB(p-C6 F4 H)2 . When used for hydrogenation of quinolines, these catalysts give excellent yields and enantiomeric excesses, and show turnover numbers of up to 460. The most attractive feature of these metal-free hydrogenation reactions was the broad functional-group tolerance, making this method complementary to existing methods for quinoline hydrogenation.
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The pathogenesis of glioma has remained unclear. In this study, it was found that high expression of the outer dense fibers of sperm tail 3B (ODF3B) in gliomas was positively correlated with the grade of glioma. The higher the grade, the worse the prognosis. ODF3B is closely related to the growth and apoptosis of glioma. In terms of mechanism, ODF3B was found to affect the proliferation and apoptosis of glioma through the JAK1 and JAK2/STAT3 pathways. ODF3B was also found to affect the growth and apoptosis of glioma in vivo. We conclude that ODF3B affects glioma proliferation and apoptosis via the JAK/STAT pathway and is a potential therapeutic target.
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A high-resolution emission inventory of anthropogenic active volatile organic compounds (VOCs) for the Yangtze River Delta (YRD) region was developed based on the local measurement of 41 cities in the region and the specific 4.4 database of EPA. The emission characteristics and composition of VOCs were analyzed. The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAP) of VOCs were calculated. The results showed that the total emission of anthropogenic VOCs in the YRD in 2017 was 4.9×106 t. The emission contributions of process sources, industrial solvent sources, mobile sources, domestic sources, storage and transportation sources, agricultural sources, and waste treatment sources were 34.3%, 27.1%, 19.5%, 9.7%, 6.1%, 2.5%, and 0.4%, respectively. Aromatic hydrocarbons and alkanes were the main components of VOCs, accounting for 25% of the total VOCs emissions in the region. The contribution rates of OFP from process sources, industrial solvent sources, mobile sources, and domestic sources were 38.3%, 21.5%, 16.4%, and 13.2%, respectively, and the contribution rates of SOAP were 26.2%, 34.1%, 18.1%, and 17.9%, respectively, which was basically consistent with the main contribution sources of VOCs emissions. The emission characteristics of the key industries in each city were obviously different. The key urban agglomeration of VOCs emission was mainly petrochemical industries and equipment manufacturing, whereas the northern part of the region was mainly wood furniture and other coating industries. The results showed that propylene, m-xylene, p-xylene, and ethylene were the main contribution sources of ozone, whereas toluene, 1,2,4-trimethylene, m-xylene, and p-xylene were the main contribution sources of secondary organic aerosols. In the next stage, the fine management of VOCs can be transformed into the main industries based on chemical reaction activity, which can give priority to the governance of key industries such as the chemical industry, petrochemical, automobile manufacturing, textile, wood, and furniture and can formulate different governance paths according to urban characteristics.
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Contaminantes Atmosféricos , Ozono , Compuestos Orgánicos Volátiles , Compuestos Orgánicos Volátiles/análisis , Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente , Ozono/análisis , Solventes , Aerosoles/análisis , ChinaRESUMEN
BACKGROUND: Metastasis to the penis is an unusual event, and penile metastasis from rectal carcinoma (PMRC) is extremely rare and associated with a dismal prognosis. Thus far, approximately 80 cases have been reported. CASE SUMMARY: Herein, we report the case of a 49-year-old man with PMRC. The patient presented to the urology clinic with a complaint of penile pain during urination. The patient underwent the Dixon operation for rectal carcinoma 2 mo before the presentation. During hospitalisation, abdominal computed tomography revealed a nodular lesion on the left penis. The postoperative pathological examination revealed a typical intestinal-type adenocarcinoma. Previous cases of PMRC were retrieved from PubMed to characterise the clinicopathological features and identify the prognostic factors of PMRC. CONCLUSION: The analysis suggested that approximately 24 mo is the median time to metastasis occurrence and 150 d is the survival time after diagnosis. Furthermore, poor pathological differentiation, lymph node involvement of the primary RC, metastasis time < 6 mo, penile metastatic nodule diameter > 1 cm, and treatment abandonment are negative predictors of survival outcomes. Close follow-up, surgical resection, chemotherapy, and radiotherapy may potentially improve the prognosis of patients.
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ortho-Selective carbene C-H insertion of unprotected phenols is achieved with dimethyl diazomalonate under the catalysis of [Rh(COD)Cl]2. After the C-H insertion, subsequent cyclization and electrophilic addition of another carbene molecule affords tris-carboxylate-substituted 2-benzofuranones as the final reaction products. The enantioselective variant has been developed with the use of chiral diene ligands. Mechanistic experiments indicate that a transient oxonium ylide directing group might be responsible for the regiocontrol at the C-H activation step.
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Nav1.7 is closely associated with neuropathic pain. Hydrogen sulfide (H2S) has recently been reported to be involved in numerous biological functions, and it has been shown that H2S can enhance the sodium current density, and inhibiting the endogenous production of H2S mediated by cystathionine ßsynthetase (CBS) using O(carboxymethyl)hydroxylamine hemihydrochloride (AOAA) can significantly reduce the expression of Nav1.7 and thus the sodium current density in rat dorsal root ganglion (DRG) neurons. In the present study, it was shown that the fluorescence intensity of H2S was increased in a spared nerve injury (SNI) model and AOAA inhibited this increase. Nav1.7 is expressed in DRG neurons, and the expression of CBS and Nav1.7 were increased in DRG neurons 7, 14 and 21 days postoperation. AOAA inhibited the increase in the expression of CBS, phosphorylated (p)MEK1/2, pERK1/2 and Nav1.7 induced by SNI, and U0126 (a MEK blocker) was able to inhibit the increase in pMEK1/2, pERK1/2 and Nav1.7 expression. However, PF04856264 did not inhibit the increase in CBS, pMEK1/2, pERK1/2 or Nav1.7 expression induced by SNI surgery. The current density of Nav1.7 was significantly increased in the SNI model and administration of AOAA and U0126 both significantly decreased the density. In addition, AOAA, U0126 and PF04856264 inhibited the decrease in rheobase, and the increase in action potential induced by SNI in DRG neurons. There was no significant difference in thermal withdrawal latency among each group. However, the time the animals spent with their paw lifted increased significantly following SNI, and the time the animals spent with their paw lifted decreased significantly following the administration of AOAA, U0126 and PF04856264. In conclusion, these data show that Nav1.7 expression in DRG neurons is upregulated by CBSderived endogenous H2S in an SNI model, contributing to the maintenance of neuropathic pain.