ABSTRACT
Transition-metal-catalyzed double/triple bond metathesis reactions have been well-established due to the ability of transition-metal catalysts to readily interact with π bonds, facilitating the progression of the entire reaction. However, activating σ-bonds to induce σ-bond metathesis is more challenging due to the absence of π bonds and the high bond energy of σ bonds. In this study, we present a novel photo-induced approach that does not rely on transition metals or photosensitizers to drive C-C and C-N σ-bond metathesis reactions. This method enables the cross-coupling of tertiary amines with α-diketones via C-C and C-N single bonds cleavage and recombination. Notably, our protocol exhibits good compatibility with various functional groups in the absence of transition metals and external photosensitizers, resulting in the formation of aryl alkyl ketones and aromatic amides in good to high yields. To gain insights into the mechanism of this pathway, we conducted controlled experiments, intermediate trapping experiments, and DFT (Density Functional Theory) calculations. This comprehensive approach allowed us to elucidate the detailed mechanism underlying this transformative reaction.
ABSTRACT
Lignin, the second largest component of biomass, is considered as an important alternative source of fossil reserves for the production of fuels and chemicals. Here, we developed a novel method to oxidatively degrade organosolv lignin into value-added four-carbon esters, particularly diethyl maleate (DEM), with the cooperative catalyst consisting of 1-(3-sulfobutyl) triethylammonium hydrogen sulfate ([BSTEA]HSO4) and 1-butyl-3-methylimidazolium ferric chloride ([BMIM]Fe2Cl7). Under optimized conditions (1.00 MPa initial O2 pressure, 160 °C, 5 h), the lignin aromatic ring was effectively cleaved by oxidation to form DEM with a yield of 15.85% and a selectivity of 44.25% in the presence of the synergistic catalyst of [BMIM]Fe2Cl7-[BSMIM]HSO4 (1/3, mol/mol). The structure and composition analysis of lignin residues and liquid products confirmed that the aromatic units in lignin were effectively and selectively oxidized. Furthermore, the catalytic oxidation of lignin model compounds was explored for obtaining a possible reaction pathway of oxidative cleavage of lignin aromatic units to DEM. This study provides a promising alternative method for the production of traditional petroleum-based chemicals.
Subject(s)
Ionic Liquids , Ionic Liquids/chemistry , Lignin/chemistry , Triticum , Catalysis , Oxidative StressABSTRACT
The facile, green, and efficient strategy for the separation of lignin from straw and subsequent production of value-added chemicals is crucial to the current utilization of straw. Herein, up to 23.72% of lignin was isolated from wheat stalk over cheap and green 1-(3-sulfobutyl) triethylammonium hydrogen sulfate ([BSTEA]HSO4) in aqueous ethanol (Vethanol: Vwater = 4:1). The acquired lignin was verified as a p-hydroxyphenyl-guaiacyl-syringyl type, which had a narrower molecular weight distribution, better thermal stability, and higher purity compared with those of the lignin obtained using 1-methyl-3-(4-sulfobutyl)-imidazolium hydrogen sulfate and 1-(3-sulfobutyl) pyridinium hydrogen sulfate. Moreover, a carbohydrate-rich liquid containing [BSTEA]HSO4 was obtained by water removal from the waste liquid after lignin separation and further converted to ethyl levulinate (EL) by a one-pot process in the presence of inexpensive and stable USY zeolite. The yield of EL reached 30.23% at 200 °C for 60 min over the presence of 40% [BSTEA]HSO4 and 60% USY zeolite. Under optimal conditions, the yields of lignin and EL can respectively reach 83.89 and 72.28% of those catalyzed by a fresh catalyst after five cycles. In short, the above-mentioned methods present a green, economic, and efficient route for the extraction of lignin and further treatment of the liquid waste generated during the extraction process.
Subject(s)
Lignin , Zeolites , Lignin/chemistry , Triticum/chemistry , Ethanol/chemistry , Water , Hydrogen , SulfatesABSTRACT
Reversible splenial lesion syndrome (RESLES) is a rare clinico-radiological disorder syndrome with unclear pathophysiology. Here, two sisters with sensorineural deafness as the chief complaint diagnosed with RESLES was reported. Although the sisters had the disease successively, they were divided into two types on imaging by isolated lesions of splenium of the corpus callosum (SCC) and extensive lesions of the corpus callosum. The clinical manifestations and lesions on MRI disappeared after 6 months. The sensorineural deafness of the sisters in this article may be caused by transcallosal auditory pathway (TCAP) injury. Auditory handicap has been found in previous RESLES cases, indicating that we know little about the connection between the SCC and the auditory pathway, and further research is needed.
ABSTRACT
We report a case with rare signs of subcutaneous hematoma, ecchymoses, and pleural effusion resulting from rupture of a thoracic aneurysm and aortic dissection. An 81-year-old woman had a history of aneurysm for 4 years. Ruptured chronic thoracic aortic dissection was diagnosed in the patient. After 2 weeks of medical therapy, the hematoma in the chest wall was absorbed, the pleural effusion almost disappeared, and the patient's general condition improved. At 6 months follow-up, the patient had no chest discomfort. This case highlights an uncommon sign of ruptured thoracic aneurysm and aortic dissection that clinicians should be aware of.
Nous décrivons un cas où la rupture d'un anévrisme de l'aorte thoracique et une dissection aortique ont été précédés de signes rares, soit un hématome sous-cutané, des ecchymoses et un épanchement pleural. Une femme âgée de 81 ans présentait des antécédents d'anévrisme depuis 4 ans. Cette patiente a reçu le diagnostic de dissection chronique de l'aorte thoracique et de rupture aortique. Après 2 semaines de traitement médical, l'hématome de la paroi thoracique s'était résorbé et l'épanchement pleural était pratique disparu. L'état général de la patiente s'est amélioré. Au suivi à 6 mois, la patiente ne présentait aucune gêne dans la poitrine. Ce cas met en lumière des signes peu courants de la rupture d'un anévrisme de l'aorte thoracique et de dissection aortique dont les cliniciens doivent avoir connaissance.
ABSTRACT
OBJECTIVE: To determine the survival rate of HIV/AIDS patients after receiving free antiretroviral treatment in Dehong prefecture, Yunnan province. METHODS: A retrospective cohort analysis was conducted on all the HIV/AIDS patients aged over 16 years who had started antiretroviral treatment during January 2007 throughout December 2009 in Dehong prefecture. RESULTS: A total of 3103 HIV/AIDS patients had received antiretroviral treatment during the study period. Among them, the mean age was (36.0 ± 9.9) years and 62.4% were males. 66.2% of them were infected with HIV through heterosexual transmission, and the mean treatment follow-up time was 21.7 months. Most patients well complied with the treatment, i.e., the average times of not taking the medicine were less than 5 per month. The cumulative survival rate of antiretroviral treatment after 1, 2, 3, 4, and 5 years were 0.95, 0.94, 0.93, 0.92, and 0.92, respectively. Data from the Cox proportional hazard regression model analysis indicated that, after adjustment for age, gender, and marital status, the baseline CD4(+)T cell counts and transmission route could significantly predicate the rates of survival. Those who were with baseline CD4(+)T cell counts as 200 - 350/mm(3)were less likely to die of AIDS than those with CD4(+) T cell counts < 200/mm(3) (Hazard Ratio or HR = 0.16, 95%CI: 0.09 - 0.28), and HIV-infected through mother-to-child transmission or routes other than heterosexual transmission were less likely to die of AIDS than through injecting drug use (HR = 0.35, 95%CI: 0.13 - 1.00). CONCLUSION: Free antiretroviral treatment had significantly improved the survival of HIV/AIDS patients. Earlier initiation of antiretroviral treatment was likely to have achieved better survival effects.