Direct synthesis of N‐(hetero)arylated heteroarenes has been realized through Cu‐mediated C−N coupling of NH azaheterocycles with aryl C−H bonds under aerobic conditions. This method features a broad ...scope of both heterocyclic arenes (pyridine, quinoline, pyrazole, imidazole, furan, thiophene, benzofuran, and indole) and NH azaheterocycles (imidazole, pyrazole, indole, azindole, purine, indazole, benzimidazole, pyridone, carbazole), providing a versatile method for the synthesis of pharmaceutically important N‐(hetero)arylated heteroarenes. The versatility of this reaction was further demonstrated through late‐stage modification of marketed drugs and the synthesis of a key intermediate for accessing a class of angiotensin II receptor 1 antagonists.
N‐(hetero)arylated heteroarenes were synthesized through Cu‐mediated C−H amination with NH azaheterocycles. This directing‐group (DG)‐mediated reaction proceeds with air as the sole oxidant, and its outstanding compatibility with heterocycles enables late‐stage diversification of a wide range of drug compounds containing multiple heterocycles.
Subtle but important differences are identified between the 1997/1998 and 2015/2016 extreme El Niños that reflect fundamental differences in their underlying dynamics. The 1997/1998 event is found to ...evolve following the eastern Pacific El Niño dynamics that relies on basin‐wide thermocline variations, whereas the 2015/2016 event involves additionally the central Pacific (CP) El Niño dynamics that depends on subtropical forcing. The stronger CP dynamics during the 2015/2016 event resulted in its sea surface temperature (SST) anomalies lingering around the International Date Line during the decaying phase, which is in contrast to the retreat of the anomalies toward the South American Coast during the decaying phase of the 1997/1998 event. The different SST evolution excited different wave trains resulting in the western U.S. not receiving the same above‐normal rainfall during the 2015/2016 El Niño as it did during the 1997/1998 El Niño. Ensemble model experiments are conducted to confirm the different climate impacts of the two El Niños.
Key Points
The 1997/1998 event is the strongest EP El Niño, while the 2015/2016 event is the strongest mixed EP and CP El Niño ever recorded
The two events exhibit subtle differences in their equatorial SST evolution that reflects fundamental differences in the underlying dynamics
The SST differences led to large differences in tropical convection, resulting in different impacts on North American climate
An extremely high degree of circularly polarized photoluminescence (CPPL) and electroluminescence (CPEL) (dissymmetry factor values: |gPL| = 0.72 and |gEL| = 1.13) are generated from twisted stacking ...of achiral conjugated polymer induced by nonemitting chiral dopant of high helical twisting power for the first time. Using a theoretical analysis incorporating the Stokes parameter, the twisting angle and birefringence of the aligned conjugated polymer, and the degree of linear polarization in the emitted light are found to make a roughly equal contribution to the degree of CPEL as to the degree of CPPL. Moreover, it is also found that the location of the recombination zone within the emitting layer is a crucial parameter for determining the difference in the dissymmetry factor between CPEL and CPPL. This result is applied to an organic light‐emitting display to improve the luminous efficiency by 60%.
Highly circularly polarized electroluminescence (|gEL| = 1.13) is generated from twisted stacking of achiral conjugated polymer induced by nonemitting chiral dopant of high helical twisting power. The location of the recombination zone is a crucial parameter for determining the degree of circular polarization. The result is applied to an organic light‐emitting display to improve the luminous efficiency by 60%.
The design of synthetic routes by retrosynthetic logic is decisively influenced by the transformations available. Transition‐metal‐catalyzed C−H activation has emerged as a powerful strategy for C−C ...bond formation, with myriad methods developed for diverse substrates and coupling partners. However, its uptake in total synthesis has been tepid, partially due to their apparent synthetic intractability, as well as a lack of comprehensive guidelines for implementation. This Review addresses these issues and offers a guide to identify retrosynthetic opportunities to generate C−C bonds by C−H activation processes. By comparing total syntheses accomplished using traditional approaches and recent C−H activation methods, this Review demonstrates how C−H activation enabled C−C bond construction has led to more efficient retrosynthetic strategies, as well as the execution of previously unattainable tactical maneuvers. Finally, shortcomings of existing processes are highlighted; this Review illustrates how some highlighted total syntheses can be further economized by adopting next‐generation ligand‐enabled approaches.
The advent of new synthetic methods has historically motivated the evolution of retrosynthetic logic. A significant recent advance is C−C bond formation enabled by C−H activation, but it has only seen modest application in synthesis. This Review compares traditional synthetic routes towards complex targets with reconceptualized ones utilizing C−H activation, highlighting the strategic advantages of this powerful approach.
The inhibition of the Anammox process: A review Jin, Ren-Cun; Yang, Guang-Feng; Yu, Jin-Jin ...
Chemical engineering journal (Lausanne, Switzerland : 1996),
07/2012, Volume:
197
Journal Article
Peer reviewed
► The inhibition of Anammox by substrates, organic matter, salts, heavy metals, phosphate and sulfide is reviewed. ► The inhibitory mechanisms of ammonia, nitrite, nontoxic organic matter and toxic ...organic matter are discussed. ► Control strategies for dealing with the inhibition problems of Anammox are presented. ► Future research prospects for Anammox inhibition are outlined.
Anaerobic ammonium oxidation (Anammox), a process ideally suited for the treatment of nitrogen-rich wastewater streams, is a promising novel biological nitrogen elimination process with attractive application prospects. However, the Anammox process is inhibited by many factors, which prevent improvements on the process as well as the application of the Anammox process. A variety of inhibitory substances, such as substrates (ammonia and nitrite), organic matter (nontoxic organic matter and toxic organic matter), salts, heavy metals, phosphate and sulfide, are commonly present in the practical applications. We conducted a detailed review of previous researches on the inhibition of Anammox processes. As a result of differences in operating conditions, experimental methods, physical structures of sludge (flocculent sludge, biofilm or granular sludge) and microbial populations involved, the effect of inhibitors varies widely. Temperature and pH adjustments, dissolved oxygen and oxidation–reduction potential controls, substrate concentration and load controls, sludge acclimatization and addition of auxiliary agents can significantly improve the performance of Anammox process under inhibitory conditions.
The removal of nitrogen from coal tar pitch (CTP) through the hydrodenitrogenation (HDN) of CTP and its molecular behavior were evaluated in the presence of NiMo/γ-alumina and CoMo/γ-alumina ...catalysts. Fourier transform ion cyclotron resonance mass spectrometry with atmospheric pressure photoionization was used to analyze the complicated chemical classes and species of CTP and the treated products at the molecular level. Nitrogen species were qualitatively analyzed before and after hydrotreatment. A single-stage hydrotreatment with an HDN catalyst resulted in a high sulfur removal performance (85.6-94.7%) but a low nitrogen removal performance (26.8-29.2%). Based on relative abundance analyses of nitrogen and binary nitrogen species, C
H
-N
S
was the most challenging species to remove during HDN treatment. Furthermore, prior hydrodesulfurization was combined with HDN treatment, and the dual hydrotreatments yielded a significantly improved nitrogen removal performance (46.4-48.7%).
The development of a Pd(II)-catalysed enantioselective fluorination of C(sp
)-H bonds would offer a new approach to making chiral organofluorines. However, such a strategy is particularly challenging ...because of the difficulty in differentiating prochiral C(sp
)-H bonds through Pd(II)-insertion, as well as the sluggish reductive elimination involving Pd-F bonds. Here, we report the development of a Pd(II)-catalysed enantioselective C(sp
)-H fluorination using a chiral transient directing group strategy. In this work, a bulky, amino amide transient directing group was developed to control the stereochemistry of the C-H insertion step and selectively promote the C(sp
)-F reductive elimination pathway from the Pd(IV)-F intermediate. Stereochemical analysis revealed that while the desired C(sp
)-F formation proceeds via an inner-sphere pathway with retention of configuration, the undesired C(sp
)-O formation occurs through an S
2-type mechanism. Elucidation of the dual mechanism allows us to rationalize the profound ligand effect on controlling reductive elimination selectivity from high-valent Pd species.
meta‐CH olefination of phenylacetic acid derivatives has been achieved using a commercially available nitrile‐containing template. The identification of N‐formyl‐protected glycine as the ligand ...(Formyl‐Gly‐OH) was crucial for the development of this reaction. Versatility of the template approach in accommodating macrocyclopalladation processes with different ring sizes is demonstrated.
It's T time: The title reaction has been achieved using a commercially available nitrile‐containing template. The identification of N‐formyl‐protected glycine as the ligand (Formyl‐Gly‐OH) was crucial for the development of this reaction. Versatility of the template approach in accommodating macrocyclopalladation processes with different ring sizes is demonstrated.
In chemical syntheses, the activation of carbon-hydrogen (C-H) bonds converts them directly into carbon-carbon or carbon-heteroatom bonds without requiring any prior functionalization. C-H activation ...can thus substantially reduce the number of steps involved in a synthesis. A single specific C-H bond in a substrate can be activated by using a 'directing' (usually a functional) group to obtain the desired product selectively. The applicability of such a C-H activation reaction can be severely curtailed by the distance of the C-H bond in question from the directing group, and by the shape of the substrate, but several approaches have been developed to overcome these limitations. In one such approach, an understanding of the distal and geometric relationships between the functional groups and C-H bonds of a substrate has been exploited to achieve meta-selective C-H activation by using a covalently attached, U-shaped template. However, stoichiometric installation of this template has not been feasible in the absence of an appropriate functional group on which to attach it. Here we report the design of a catalytic, bifunctional nitrile template that binds a heterocyclic substrate via a reversible coordination instead of a covalent linkage. The two metal centres coordinated to this template have different roles: one reversibly anchors substrates near the catalyst, and the other cleaves remote C-H bonds. Using this strategy, we demonstrate remote, site-selective C-H olefination of heterocyclic substrates that do not have the necessary functional groups for covalently attaching templates.
In many plant species, male-sterile female lines with cytoplasmic male sterility (CMS) or nuclear-controlled environment-sensitive genic male sterility (EGMS) have long been used to efficiently ...produce hybrids that harness hybrid vigor or heterosis. However, the underlying molecular mechanisms for these applications have only recently been uncovered in a few species. We provide here an update on the understanding of cytoplasmic–nuclear communication based on the discovery of mitochondrial CMS genes and their corresponding nuclear fertility determinants. Recent findings that uncover diverse mechanisms such as epigenetic, transcriptional, and post-transcriptional controls of EGMS by temperature and photoperiod signals are also reviewed. Furthermore, translational research that applies basic knowledge of plant male fertility control to hybrid seed production practice is highlighted.
CMS lines used for three-line hybrid system can only be recovered by a specific restorer of male fertility (Rf) gene.
CMS genes may be formed during evolution through gene duplication and multi-recombination, and the corresponding nuclear Rf genes appear to have undergone coevolution.
EGMS lines, mainly caused by nuclear gene mutations, have been developed for the two-line breeding system, particularly in rice.
Complex and diverse interactions between genetic control and environmental temperature and photoperiods may determine plant male fertility.
The identification and utilization of nuclear male-sterile genes in combination with new technologies have achieved successful male fertility control of crops.
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