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Nature Communications Jul 2022The C-F bond cleavage and C-C bond formation (i.e., carbodefluorination) of readily accessible (per)fluoroalkyl groups constitutes an atom-economical and efficient route...
The C-F bond cleavage and C-C bond formation (i.e., carbodefluorination) of readily accessible (per)fluoroalkyl groups constitutes an atom-economical and efficient route to partially fluorinated compounds. However, the selective mono-carbodefluorination of trifluoromethyl (CF) groups remains a challenge, due to the notorious inertness of C-F bond and the risk of over-defluorination arising from C-F bond strength decrease as the defluorination proceeds. Herein, we report a carbene-initiated rearrangement strategy for the carbodefluorination of fluoroalkyl ketones with β,γ-unsaturated alcohols to provide skeletally and functionally diverse α-mono- and α,α-difluoro-γ,δ-unsaturated ketones. The reaction starts with the formation of silver carbenes from fluoroalkyl N-triftosylhydrazones, followed by nucleophilic attack of a β,γ-unsaturated alcohol to form key silver-coordinated oxonium ylide intermediates, which triggers selective C-F bond cleavage by HF elimination and C-C bond formation through Claisen rearrangement of in situ generated difluorovinyl ether. The origin of chemoselectivity and the reaction mechanism are determined by experimental and DFT calculations. Collectively, this strategy by an intramolecular cascade process offers significant advances over existing stepwise strategies in terms of selectivity, efficiency, functional group tolerance, etc.
Topics: Alcohols; Ketones; Methane; Silver
PubMed: 35879307
DOI: 10.1038/s41467-022-31976-z -
Molecules (Basel, Switzerland) May 2022As one of the abundant and inexpensive metals on the earth, copper has demonstrated broad applications in synthetic chemistry and catalysis. Among these copper-catalyzed... (Review)
Review
As one of the abundant and inexpensive metals on the earth, copper has demonstrated broad applications in synthetic chemistry and catalysis. Among these copper-catalyzed advances, copper carbenes are versatile and reactive intermediates that can mediate a variety of transformations, which have attracted much attention in the past decades. The present review summarizes two different reaction models that take place between a copper carbene intermediate and alkyne species, including the cross-coupling reaction of copper carbene intermediate with terminal alkyne, and the addition of copper carbene intermediate onto the C-C triple bond. This article will cover the profile from 2010 to 2021 by placing emphasis on the detailed catalytic models and highlighting the synthetic applications offered by these practical and mild methods.
Topics: Alkynes; Catalysis; Copper; Methane
PubMed: 35630567
DOI: 10.3390/molecules27103088 -
Scientific Reports Jan 2022Fossil benthic foraminifera are used to trace past methane release linked to climate change. However, it is still debated whether isotopic signatures of living...
Fossil benthic foraminifera are used to trace past methane release linked to climate change. However, it is still debated whether isotopic signatures of living foraminifera from methane-charged sediments reflect incorporation of methane-derived carbon. A deeper understanding of isotopic signatures of living benthic foraminifera from methane-rich environments will help to improve reconstructions of methane release in the past and better predict the impact of future climate warming on methane seepage. Here, we present isotopic signatures (δC and δO) of foraminiferal calcite together with biogeochemical data from Arctic seep environments from c. 1200 m water depth, Vestnesa Ridge, 79° N, Fram Strait. Lowest δC values were recorded in shells of Melonis barleeanus, - 5.2‰ in live specimens and - 6.5‰ in empty shells, from sediments dominated by aerobic (MOx) and anaerobic oxidation of methane (AOM), respectively. Our data indicate that foraminifera actively incorporate methane-derived carbon when living in sediments with moderate seepage activity, while in sediments with high seepage activity the poisonous sulfidic environment leads to death of the foraminifera and an overgrowth of their empty shells by methane-derived authigenic carbonates. We propose that the incorporation of methane-derived carbon in living foraminifera occurs via feeding on methanotrophic bacteria and/or incorporation of ambient dissolved inorganic carbon.
Topics: Anaerobiosis; Arctic Regions; Carbon Cycle; Foraminifera; Geologic Sediments; Global Warming; Methane; Oxidation-Reduction
PubMed: 35064198
DOI: 10.1038/s41598-022-05175-1 -
Current Topics in Medicinal Chemistry 2016The fascinating chemical properties of N-heterocyclic carbene (NHC) complexes showed them to be a suitable class of complexes to be investigated for their applications... (Review)
Review
The fascinating chemical properties of N-heterocyclic carbene (NHC) complexes showed them to be a suitable class of complexes to be investigated for their applications as drugs in the treatment of the infectious disease or cancer. In particular, the great structural versatility provided a library of compounds with a low cytotoxic profile, suitable candidates as new anticancer agents. Most of these complexes have shown higher cytotoxicity than cisplatin. In the present review, the medicinal applications of copper(I)- and silver(I)-NHC complexes are summarized. Specifically, azolium precursors and related Cu(I)- and Ag(I)-NHC complexes of functionalized and non-functionalized imidazole-, and benzimidazole-based NHC complexes studied as an alternative to cisplatin as chemotherapeutic agents are reviewed. An outline of the most significant chemical features is presented: copper(I)- and silver(I)-NHC complexes tested as anticancer drugs have been reported and a description of structure-activity relationships was made as far as possible.
Topics: Chemistry, Pharmaceutical; Coordination Complexes; Copper; Heterocyclic Compounds; Methane; Silver
PubMed: 27150368
DOI: 10.2174/1568026616666160506145408 -
Drug Development Research Nov 2021Because of the continuous need for efficient therapeutic agents against various kinds of cancers and infectious diseases, the pharmaceutical industry has to find new... (Review)
Review
Because of the continuous need for efficient therapeutic agents against various kinds of cancers and infectious diseases, the pharmaceutical industry has to find new candidates and strategies to develop novel and efficient drugs. They increasingly use computational tools in R&D stages for screening extensive sets of drug candidates before starting pre-clinical and clinical trials. N-Heterocyclic carbenes (NHCs) can be evaluated as good drug candidates because they offer both anti-cancer and anti-inflammatory features with their general low-toxicity profiles. To date, different kinds of NHCs (Cu, Co, Ni, Au, Ag, Ru, etc.) have been synthesized and their therapeutic uses has been shown. Here, we have reviewed the recent studies focused on Ag(I)-NHC complexes and their anti-cancer activities. Also, existing examples of the usage of density functional theory and structure-activity relationship have been evaluated.
Topics: Heterocyclic Compounds; Methane; Neoplasms; Silver; Structure-Activity Relationship
PubMed: 33978961
DOI: 10.1002/ddr.21822 -
Chemical Society Reviews Jul 2022Transition metal-catalysed carbene- and nitrene transfer to the C1-building blocks carbon monoxide and isocyanides provides heteroallenes ( ketenes, isocyanates,... (Review)
Review
Transition metal-catalysed carbene- and nitrene transfer to the C1-building blocks carbon monoxide and isocyanides provides heteroallenes ( ketenes, isocyanates, ketenimines and carbodiimides). These are versatile and reactive compounds allowing transformation towards numerous functional groups and organic compounds, including heterocycles. Both one-pot and tandem processes have been developed providing valuable synthetic methods for the organic chemistry toolbox. This review discusses all known transition metal-catalysed carbene- and nitrene transfer reactions towards carbon monoxide and isocyanides and transformation of the heteroallenes hereby obtained, with a special focus on the general mechanistic considerations.
Topics: Carbon Monoxide; Cyanides; Imines; Methane; Transition Elements
PubMed: 35748338
DOI: 10.1039/d1cs00305d -
Molecules (Basel, Switzerland) Aug 2022This study presents a biophotocatalytic system as a sustainable technology for the recovery of clean water and renewable energy from wastewater, thereby providing a...
This study presents a biophotocatalytic system as a sustainable technology for the recovery of clean water and renewable energy from wastewater, thereby providing a unique opportunity to drive industrialization and global sustainable development throughputs. Herein, inhouse magnetized photocatalyst (Fe-TiO) with surface area 62.73 m/g synthesized via co-precipitation, was hypothesized to hasten an up-flow anaerobic sludge blanket (UASB) reactor for the treatment of local South Africa municipality wastewater with the benefit of high-quality biogas production. A lab scale UASB process with a working volume of 5 L coupled with two UV-lights (T8 blacklight-blue tube, 365 nm, 18 W) was operated batchwise under mesophilic conditions for the period of 30 days with a constant organic load charge of 2.76 kg COD/m. d. This biophotocatalytic system performance was investigated and compared with and without the Fe-TiO charge (2-6 g) with respect to effluent quality, biogas production and CO methanation. Using chemical oxygen demand (COD) measured as the degree of degradation of the pollutants, the best efficiency of 93% COD removal was achieved by a 4 g Fe-TiO charge at 14 days and pH of 7.13, as compared to zero charge where only 49.6% degradation was achieved. Under the same charge, cumulative biogas and methane content of 1500 mL/g COD.d and 85% were respectively attained as compared with the control with 400 mL/g COD.d and 65% methane content. Also, the energy produced can be used to offset the energy utilized by the UV-light for the wastewater abatement and other limitations of photocatalysis. The BP system was found to be an eco-friendly and cost-effective technology to be explored in water treatment settings.
Topics: Anaerobiosis; Biofuels; Bioreactors; Carbon Dioxide; Methane; Sewage; Titanium; Waste Disposal, Fluid; Wastewater
PubMed: 36014454
DOI: 10.3390/molecules27165213 -
Environmental Science and Pollution... Feb 2024The unprecedented population and anthropogenic activity rise have challenged the future look up for shifts in global temperature and climate patterns. Anthropogenic... (Review)
Review
The unprecedented population and anthropogenic activity rise have challenged the future look up for shifts in global temperature and climate patterns. Anthropogenic activities such as land fillings, building dams, wetlands converting to lands, combustion of biomass, deforestation, mining, and the gas and coal industries have directly or indirectly increased catastrophic methane (CH) emissions at an alarming rate. Methane is 25 times more potent trapping heat when compared to carbon dioxide (CO) in the atmosphere. A rise in atmospheric methane, on a 20-year time scale, has an impact of 80 times greater than that of CO. With increased population growth, waste generation is rising and is predicted to reach 6 Mt by 2025. CH emitted from landfills is a significant source that accounts for 40% of overall global methane emissions. Various mitigation and emissions reduction strategies could significantly reduce the global CH burden at a cost comparable to the parallel and necessary CO reduction measures, reversing the CH burden to pathways that achieve the goals of the Paris Agreement. CH mitigation directly benefits climate change, has collateral impacts on the economy, human health, and agriculture, and considerably supports CO mitigation. Utilizing the CO from the environment, methanogens produce methane and lower their carbon footprint. NGOs and the general public should act on time to overcome atmospheric methane emissions by utilizing the raw source for producing carbon-neutral fuel. However, more research potential is required for green energy production and to consider investigating the untapped potential of methanogens for dependable energy generation.
Topics: Humans; Climate Change; Carbon Dioxide; Biodiversity; Temperature; Methane
PubMed: 37884720
DOI: 10.1007/s11356-023-30601-w -
Science (New York, N.Y.) Feb 2022[Figure: see text].
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Chemical Society Reviews Apr 2022C-H functionalization has been emerging as a powerful method to establish carbon-carbon and carbon-heteroatom bonds. Many efforts have been devoted to... (Review)
Review
C-H functionalization has been emerging as a powerful method to establish carbon-carbon and carbon-heteroatom bonds. Many efforts have been devoted to transition-metal-catalyzed direct transformations of C-H bonds. Metal carbenes generated from transition-metal compounds and diazo or its equivalents are usually applied as the transient reactive intermediates to furnish a catalytic cycle for new C-C and C-X bond formation. Using this strategy compounds from unactivated simple alkanes to complex molecules can be further functionalized or transformed to multi-functionalized compounds. In this area, transition-metal-catalyzed carbene insertion to C-H bonds has been paid continuous attention. Diverse catalyst design strategies, synthetic methods, and potential applications have been developed. This critical review will summarize the advance in transition-metal-catalyzed carbene insertion to C-H bonds dated up to July 2021, by the categories of C-H bonds from aliphatic C(sp)-H, aryl (aromatic) C(sp)-H, heteroaryl (heteroaromatic) C(sp)-H bonds, alkenyl C(sp)-H, and alkynyl C(sp)-H, as well as asymmetric carbene insertion to C-H bonds, and more coverage will be given to the recent work. Due to the rapid development of the C-H functionalization area, future directions in this topic are also discussed. This review will give the authors an overview of carbene insertion chemistry in C-H functionalization with focus on the catalytic systems and synthetic applications in C-C bond formation.
Topics: Carbon; Catalysis; Methane; Transition Elements
PubMed: 35297455
DOI: 10.1039/d1cs00895a