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1.
J Hazard Mater ; 441: 129958, 2023 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-36122523

RESUMO

In recent years, Poly(butylene adipate-co-terephthalate) (PBAT) films were wildly used due to its biodegradable properties. However, there are few reports of strains that can high efficiently degrade PBAT. Thermobifida fusca FXJ-1, a thermophilic actinomycete, was screened and identified from compost. FXJ-1 can efficiently degrade PBAT at 55 °C in MSM medium. The degradation rates of the pure PBAT film (PF), PBAT film used for mulching on agricultural fields (PAF), and PBAT-PLA-ST film (PPSF) were 82.87 ± 1.01%, 87.83 ± 2.00% and 52.53 ± 0.54%, respectively, after nine days of incubation in MSM medium. Cracking areas were monitored uniformly distributed on the surfaces of three kinds of PBAT-based films after treatment with FXJ-1 using scanning electron microscopy. The LC-MS results showed that PBAT might be degraded into adipic acid, terephthalic acid, butylene adipate, butylene terephthalate and butylene adipate-co-terephthalate, and these products are involved in the cleavage of ester bonds. We also found that amylase produced by FXJ-1 played an important role in the degradation of PPSF. FXJ-1 also showed an efficient PBAT-based films degradation ability in simulating compost environment, which implied its potential application in PBAT and starch-based film degradation by industrial composting.


Assuntos
Compostagem , Poliésteres , Adipatos/química , Alcenos , Amilases , Ésteres , Ácidos Ftálicos , Poliésteres/química , Amido/química , Thermobifida
2.
J Environ Sci (China) ; 124: 723-734, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36182177

RESUMO

Understanding the emission sources of volatile organic compounds (VOCs) is critical for air pollution mitigation. Continuous measurements of atmospheric VOCs were conducted from January to February in Hangzhou in 2021. The average measured concentration of total VOCs (TVOCs) was 38.2 ± 20.9 ppb, > 42% lower than that reported by previous studies at the urban center in Hangzhou. The VOC concentrations and proportions were similar between weekdays and weekends. During the long holidays of the Spring Festival in China, the concentrations of TVOCs were ∼50% lower than those during the regular days, but their profiles showed no significant difference (p > 0.05). Further, we deduced that aromatics and alkenes were the most crucial chemicals promoting the formation of O3 and secondary organic aerosol (SOA) in Hangzhou. According to interspecies correlations, combustion processes and solvent use were inferred as major VOC emission sources. This study provides implications for air quality improvements before and during the upcoming Asian Games that will be hosted in Hangzhou in 2022.


Assuntos
Poluentes Atmosféricos , Ozônio , Compostos Orgânicos Voláteis , Aerossóis/análise , Poluentes Atmosféricos/análise , Alcenos/análise , China , Monitoramento Ambiental , Ozônio/análise , Solventes , Compostos Orgânicos Voláteis/análise
3.
J Environ Sci (China) ; 124: 794-805, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36182184

RESUMO

Both concentrations and emissions of many air pollutants have been decreasing due to implement of control measures in China, in contrast to the fact that an increase in emissions of non-methane hydrocarbons (NMHCs) has been reported. This study employed seven years continuous NMHCs measurements and the related activities data of Shanghai, a megacity in China, to explore evolution of emissions and effectiveness of air pollution control measures. The mixing ratio of NMHCs showed no statistical interannual changes, of which their compositions exhibited marked changes. This resulted in a decreasing trend of ozone formation potential by 3.8%/year (p < 0.05, the same below), which should be beneficial to ozone pollution mitigation as its production in Shanghai is in the NMHCs-limited regime. Observed alkanes, aromatics and acetylene changed by +3.7%/year, -5.9%/year and -7.4%/year, respectively, and alkenes showed no apparent trend. NMHCs sources were apportioned by a positive matrix factorization model. Accordingly, vehicular emissions (-5.9%/year) and petrochemical industry emissions (-7.1%/year) decreased significantly, but the decrease slowed down; significant reduction in solvent usage (-9.0%/year) appeared after 2010; however, emissions of natural gas (+12.6%/year) and fuel evaporation (with an increasing fraction) became more important. The inconsistency between observations and inventories was found in interannual trend and speciation as well as source contributions, emphasizing the need for further validation in NMHCs emission inventory. Our study confirms the effectiveness of measures targeting mobile and centralized emissions from industrial sources and reveals a need focusing on fugitive emissions, which provided new insights into future air policies in polluted region.


Assuntos
Poluentes Atmosféricos , Ozônio , Compostos Orgânicos Voláteis , Poluentes Atmosféricos/análise , Alcanos/análise , Alcenos/análise , Alcinos , China , Monitoramento Ambiental/métodos , Hidrocarbonetos/análise , Metano , Gás Natural , Ozônio/química , Solventes , Emissões de Veículos/análise , Compostos Orgânicos Voláteis/análise
4.
Food Chem ; 400: 134100, 2023 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-36075172

RESUMO

Poly (butylene adipate-co-terephthalate) (PBAT)/polylactic acid (PLA) blended with compatibilizers (polycaprolactone, PCL; poly (ethylene glycol), PEG; titanium dioxide, nano-TiO2) (TP@PLA composites) were developed by melt processing. Natamycin incorporated into TP@PLA blend composites formed NTP@PLA films, which exhibited high tensile strength (24.1-43.5 MPa) and elongation at break (85.8-258.2 %), and exhibited good oxygen permeability, water vapor permeability, surface hydrophobicity and biodegradability. The in vitro results revealed that inhibition of Penicillium expansum cell growth of the NTP@PLA films with addition of 1.0 wt% natamycin reached 95.72 %. The NTP@PLA film with natamycin effectively reduced incidence of decay (1.52 %) on grapes, maintained their quality, and inhibited the growth of pathogenic fungi to up to 0.42 log cfu·g-1. This study generates new insights into the preservation properties of antimicrobial NTP@PLA film, which endow it with great application potential as a novel and eco-friendly packaging material for the food industry.


Assuntos
Anti-Infecciosos , Vitis , Adipatos , Alcenos , Antibacterianos , Anti-Infecciosos/farmacologia , Etilenoglicóis , Ácido Láctico , Natamicina , Oxigênio , Ácidos Ftálicos , Poliésteres , Vapor , Titânio
5.
Nat Commun ; 13(1): 6861, 2022 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-36369422

RESUMO

Enantioenriched N-alkylindole compounds, in which nitrogen is bound to a stereogenic sp3 carbon, are an important entity of target molecules in the fields of biological, medicinal, and organic chemistry. Despite considerable efforts aimed at inventing methods for stereoselective indole functionalization, straightforward access to a diverse range of chiral N-alkylindoles in an intermolecular catalytic fashion from readily available indole substrates remains an ongoing challenge. In sharp contrast to existing C-N bond-forming strategies, here, we describe a modular nickel-catalyzed C-C coupling protocol that couples a broad array of N-indolyl-substituted alkenes with aryl/alkenyl/alkynyl bromides to produce chiral N-alkylindole adducts in single regioisomeric form, in up to 91% yield and 97% ee. The process is amenable to proceed under mild conditions and exhibit broad scope and high functional group compatibility. Utility is highlighted through late-stage functionalization of natural products and drug molecules, preparation of chiral building blocks.


Assuntos
Alcenos , Níquel , Níquel/química , Estereoisomerismo , Catálise , Alcenos/química , Indóis
6.
Org Lett ; 24(44): 8233-8238, 2022 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-36326444

RESUMO

Herein, we report a CuH-catalyzed asymmetric desymmetrization of prochiral cyclopentane-1,3-diones to access cyclic 3-hydroxy ketones having an all-carbon quaternary center with high diastereoselectivity via hydrosilylation using PMHS as an inexpensive hydride source. This reaction displays high functional group tolerance including reducible alkyne, alkene, and ester groups with a broad substrate scope. The importance of chiral cyclic 3-hydroxy ketone building blocks was also demonstrated through the synthesis of (-)-estrone, the toxicodenane E core, and fused indoles.


Assuntos
Alcenos , Cetonas , Estereoisomerismo , Catálise , Indóis
7.
Molecules ; 27(21)2022 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-36364041

RESUMO

Cis-alkenes are ubiquitous in biological molecules, which makes it greatly significant to develop efficient methods toward construction of cis-olefins. Herein, we reported a facile semi-hydrogenation of alkynes to cis-alkenes in an efficient way with cuprous bromide/tributylphosphine as the catalyst and bis(pinacolato)diboron/methanol as the hydrogen donor. The method features convenient and facile reaction conditions, wide substrate scope, high yields, and high stereoselectivity.


Assuntos
Alcinos , Cobre , Alcinos/química , Cobre/química , Hidrogenação , Alcenos/química , Catálise
8.
Molecules ; 27(21)2022 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-36364093

RESUMO

The factors that affect acceleration and high trans/cis selectivity in the catalytic cyclopropanation reaction of styrene with ethyl diazoacetate by cobalt N-confused porphyrin (NCP) complexes were investigated using density functional theory calculations. The reaction rate was primarily related to the energy gap between the cobalt-carbene adduct intermediates, A and B, which was affected by the NCP skeletons and axial pyridine ligands more than the corresponding porphyrin complex. In addition, high trans/cis stereoselectivity was determined at the TS1 and, in part, in the isomerization process at the carbon-centered radical intermediates, Ctrans and Ccis.


Assuntos
Porfirinas , Ligantes , Cobalto , Carbono , Alcenos
9.
Org Lett ; 24(45): 8452-8457, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36342386

RESUMO

An efficient approach for the synthesis of phenanthrene scaffolds by utilizing the dual catalytic activity of an organo-photocatalyst is documented. The controlled cascade transformation proceeds via in situ diazotization followed by olefin isomerization and subsequent arene radical generation through photoreduction. The overall process demonstrates both the photosensitization and photoredox properties of a single organo-photocatalyst and facilitates the desired intramolecular annulation with high precision and efficacy. In this context, the underexplored organocatalyst acridine orange base is employed and the photophysical interactions between the catalyst and the substrates along with the detailed reaction kinetics are documented.


Assuntos
Luz , Fenantrenos , Oxirredução , Catálise , Alcenos/química , Fenantrenos/química
10.
Org Lett ; 24(45): 8370-8374, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36350067

RESUMO

A highly diastereo- and enantioselective formal [4 + 2] cyclization of α,ß-unsaturated ketoesters with nitroalkenes through a tandem asymmetric Michael addition-intramolecular Henry reaction under dihydroquinine-based phase-transfer catalysis, leading to a one-pot construction of four contiguous stereochemical centers and multiple functional groups with excellent diastereo- and enantioselectivities in high yields, has been developed. The ee values of some products were increased to ∼100% in good yields after one crystallization.


Assuntos
Alcenos , Nitrocompostos , Ciclização , Estereoisomerismo , Alcenos/química , Catálise , Nitrocompostos/química
11.
Org Lett ; 24(45): 8343-8347, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36350256

RESUMO

gem-Bromofluoroalkenes have been combined with phosphite under irradiation, in the presence of Fukuzumi's catalyst (9-mesityl-10-methylacridinium perchlorate) as an organic photocatalyst, to provide valuable gem-fluorophosphonate derivatives, known as stable mimics of phosphates. The desired products were obtained in good to excellent yields, and the reaction showed very good chemical tolerance.


Assuntos
Alcenos , Estrutura Molecular , Catálise
12.
J Org Chem ; 87(22): 15511-15529, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36318193

RESUMO

We developed a visible-light-mediated [3 + 2] cycloaddition of arylcyclopropylamine with structurally diverse olefins using QXPT-NPh as a highly efficient organic photoredox catalyst. We first achieved the use of various alkyl-substituted alkenes in intermolecular [3 + 2] cycloadditions with cyclopropylamine. We also developed a general and efficient strategy for the construction of structurally diverse cyclopentane-based spiro[4.n] skeletons with 1,3-difunctional groups, which broadly exist in natural products and synthetic molecules. Furthermore, we proposed a hydrogen-bond mode between the arylcyclopropylamine and the photocatalyst QXPT-NPh.


Assuntos
Alcenos , Esqueleto , Reação de Cicloadição , Alcenos/química , Estrutura Molecular
13.
J Org Chem ; 87(22): 15415-15420, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36318761

RESUMO

Starting from ortho-bromostyrenes, 12 6,7-benzotropolones were synthesized in 3 or 4 steps. Br/Li exchanges provided the respective ortho-lithiostyrenes. The latter were acylated by a Weinreb amide, if unhindered, or hydroxyalkylated by an aldehyde, if hindered (an oxidation ensuing thereafter). Acetonide-containing benzannulated nonatrienones resulted. Ring-closing olefin metatheses converted them into acetonide-containing benzocycloheptadienones. Treatment with aq. HCl caused hydrolyses followed by ß-elimination reactions giving 6,7-benzotropolones.


Assuntos
Biflavonoides , Hidrólise , Alcenos , Acilação
14.
J Org Chem ; 87(22): 15608-15617, 2022 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-36321171

RESUMO

This article presents an exploration of stereospecificity and divergent reactivity of Pd-catalyzed α,α-disubstituted alkenyl hydrazones to synthesize 1,4-dienes in the Z configuration and vinylcyclopropane. We calculated the energy profiles of four α,α-disubstituted alkenyl hydrazones. The results show that the energy profiles of the whole catalytic cycle are basically the same before the syn-carbopalladation step. Subsequent syn-ß-C elimination yields skipping dienes, or direct ß-H elimination yields vinylcyclopropane. Current theoretical calculations reveal that the stereospecificity and the divergent reactivity of reactions result from the competition between syn-ß-C elimination and ß-H elimination. The C-C bond rotation and subsequent syn-ß-C elimination step control the stereospecificity of the reaction by changing the olefin stereostructure from E to Z configuration. The steric factor of α-substituted groups mediates the transformation between syn-ß-C elimination and ß-H elimination. The results are of great significance for the scientific design of substrates to achieve accurate synthesis of target products.


Assuntos
Hidrazonas , Paládio , Paládio/química , Estereoisomerismo , Alcenos/química , Catálise
15.
Org Lett ; 24(46): 8503-8508, 2022 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-36367970

RESUMO

Enantioselective cyclopropanation of α-carbonyl sulfoxonium ylides (SY) has so far been limited to addition/ring closure reactions on electron-poor olefins. Herein, we report the iridium-catalyzed intramolecular cyclopropanation of SY in the presence of a chiral diene in up to 96% yield and 98% enantioselectivity. Moreover, density functional theory calculations suggest that the re face of the olefin preferably attacks an iridium carbene intermediate in an asynchronous concerted step that is independent of the geometry of the olefin.


Assuntos
Alcenos , Irídio , Estereoisomerismo , Catálise
16.
J Am Chem Soc ; 144(46): 21287-21294, 2022 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-36346832

RESUMO

To optimize the performance of supported olefin polymerization catalysts, novel methodologies are required to evaluate the composition, structure, and morphology of both pristine and prepolymerized samples in a resource-efficient, high-throughput manner. Here, we report on a unique combination of laboratory-based confocal fluorescence microscopy and advanced image processing that allowed us to quantitatively assess support fragmentation in a large number of autofluorescent metallocene-based catalyst particles. Using this approach, significant inter- and intraparticle heterogeneities were detected and quantified in a representative number of prepolymerized catalyst particles (2D: ≥135, 3D: 40). The heterogeneity that was observed over several stages of slurry-phase ethylene polymerization (10 bar) is primarily attributed to the catalyst particles' diverse support structures and to the inhomogeneities in the metallocene distribution. From a mechanistic point of view, the 2D and 3D analyses revealed extensive contributions from a layer-by-layer fragmentation mechanism in synergy with a less pronounced sectioning mechanism. A significant number of catalyst particles were also found to display limited support fragmentation at the onset of the reaction (i.e., at lower polymer yields). This delay in activity or "dormancy" is believed to contribute to a broadening of the particle size distribution during the early stages of polymerization. 2D and 3D catalyst screening via confocal fluorescence microscopy represents an accessible and fast approach to characterize the structure of heterogeneous catalysts and assess the distribution of their fluorescent components and reaction products. The automation of both image segmentation and postprocessing with machine learning can yield a powerful diagnostic tool for future research as well as quality control on industrial catalysts.


Assuntos
Alcenos , Polimerização , Alcenos/química , Metalocenos , Catálise , Microscopia de Fluorescência
17.
J Am Chem Soc ; 144(46): 21206-21212, 2022 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-36346682

RESUMO

Polyolefins constitute the majority of plastics produced worldwide. Despite the variety of precatalyst activation mechanisms known in the literature, the development of spatially controlled olefin polymerizations remains relatively unknown. If successful, control over the olefin polymerization process could provide unprecedented synthetic control and potentially broaden industrial applications. Herein, we demonstrate a simple olefin polymerization methodology termed photoinduced initiation of olefin polymerization (PIOP), wherein photoacid generators are used in conjunction with controlled irradiation to achieve precatalyst activation and olefin polymerization. These results demonstrate that PIOP can be used for solution-based polymerizations of ethylene and α-olefins and may be extended to heterogeneous polymerizations of gaseous ethylene and propylene, thereby achieving spatial control over the olefin polymerization process.


Assuntos
Alcenos , Etilenos , Polimerização , Catálise
18.
J Am Chem Soc ; 144(41): 18803-18809, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-36194776

RESUMO

A method for the regiodivergent aminooxygenation of aryl olefins under electrophotocatalytic conditions is described. The procedure employs a trisaminocyclopropenium (TAC) ion catalyst with visible light irradiation under a controlled electrochemical potential to convert aryl olefins to the corresponding oxazolines with high chemo- and diastereoselectivity. With the judicious choice between two inexpensive and abundant reagents, namely water and urethane, either 2-amino-1-ol or 1-amino-2-ol derivatives could be prepared from the same substrate. This method is amenable to multigram synthesis of the oxazoline products with low catalyst loadings.


Assuntos
Alcenos , Uretana , Catálise , Indicadores e Reagentes , Água
19.
J Am Chem Soc ; 144(41): 18761-18765, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-36197795

RESUMO

The reaction of W(NAr)(13C4H8)(OSiPh3)2 (1) (NAr = 2,6-diisopropylphenylimido) with silica partially dehydroxylated at 700 °C (SiO2-700) is highly dependent on the reaction conditions. The primary product of this reaction is W(NAr)(13C4H8)(OSiPh3)(OSi(O-)3) (2) when the reaction is carried out in the dark. Grafting 1 onto SiO2-700 in ambient lab light results in the formation of 2, W(NAr)(13CH213CH2)(OSiPh3)(OSi(O-)3) (4), and one isomer of square-pyramidal W(NAr)(13CH213CH(13Me)13CH2)(OSiPh3)(OSi(O-)3) (3). Heating 2 to 85 °C for 6 h results in the formation of 3, 4, W(NAr)(13CH(13Me)13CH213CH2)(OSiPh3)(OSi(O-)3) (5), and W(NAr)((13CH2)213CH(13Me)(13CH2)2)(OSiPh3)(OSi(O-)3) (6). Photolysis of 2 with blue LEDs (λmax = 450 nm) produces 4, both isomers of 3, 5, and free ethylene. In the presence of excess ethylene and blue LED irradiation at 85 °C, 1/SiO2-700 catalyzes the direct conversion of ethylene to propylene.


Assuntos
Alcenos , Dióxido de Silício , Etilenos
20.
J Am Chem Soc ; 144(41): 19173-19185, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-36198090

RESUMO

Detailed herein are our synthetic studies toward the preparation of the C18- and C19-benzenoid cephalotane-type norditerpenoids. Guided by chemical network analysis, the core structure of this natural product family was constructed in a concise manner using an iterative cross-coupling, followed by a formal inverse-electron-demand [4 + 2] cycloaddition. Initial efforts to functionalize an alkene group in the [4 + 2] cycloadduct using a Mukaiyama hydration and a subsequent olefination led to the complete C18-carbon framework. While effective, this approach proved lengthy and prompted the development of a direct alkene difunctionalization that relies on borocupration to advance the cycloadduct to the natural products. Late-stage peripheral C-H functionalization facilitated access to all of the known cephanolides in 6-10 steps as well as five recently isolated ceforalides in 8-13 steps.


Assuntos
Produtos Biológicos , Diterpenos , Diterpenos/química , Reação de Cicloadição , Alcenos , Carbono/química
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