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The 4-alkylidene-tetrahydroquinoline was constructed via a vinylogous cascade condensation/[1,7]-HT/6-endo-trig cyclization strategy, which features a novel product skeleton, high chemoselectivity & diastereoselectivity, facile introduction of 4-alkylidenyl motifs.

An aromatization-driven hydride transfer-involved α-C(sp3)–H bond functionalization of the oxygen atom was developed. Easily prepared p-quinone methides were applied to initiate [1,5]-hydride transfer/cyclization for generating spirochromanes.

Recent studies have shown that layered compound EuCd2As2 could exhibit diverse topological states depending on the different magnetic structures, such as Weyl semimetal, Dirac semimetal, topological insulator, etc. In order to further study the interplay between magnetism and topology of EuCd2As2, it is necessary to figure out its magnetic structure. Here, by magnetization (M) measurements and negative magnetostriction (λ) along the [001] direction measured by scanning tunneling microscope on EuCd2As2 single crystals, we observe field-induced metamagnetic phase transition from A-type antiferromagnetic (AFM) ground state to field-polarized state, with canted AFM (CAFM) state in between. Magnetization and magnetostriction are more sensitive to the in-plane field than the out-of-plane field, indicating the magnetic moments lying in the ab plane. The absence of abrupt jump on M-H and λ-H curves demonstrates the phase transition is a second-order type. In CAFM state, M increases linearly with the field and λ is proportional to M 2 . Tunneling conductance spectra show the field-induced evolution of the electronic density of states. Our results provide experimental evidence for understanding the magnetic structure of EuCd2As2.

Switchable construction of oxa-heterocycles with diverse ring sizes has been developed by performing dibrominated-compound-controlled chemoselective cyclization and subsequent derivatization.

This review highlights the encouraging advances in hydride transfer-involved dearomatization reaction during the past decade, the content of which is categorized according to the hydride acceptors, namely vinylogous imines and quinone methides.

The three-component reaction of o-aminobenzaldehydes with 5-hydroxyindole and electron-rich arenes has been achieved through HFIP-mediated cascade hydride transfer/dearomative cyclization/CDC-type imidization at room temperature under air.

The scaffolds of 2,3-dihydroquinolin-4-one and benzoazepine-5-one were controllably constructed relying on cascade condensation/redox-neutral [1,6]/[1,7]-hydride transfer/cyclization from 2-aminoacetophenone and various aldehydes as well as isatins.

The 2,3-dihydroquinolin-4-one scaffolds were constructed diastereoselectively via cascade Knoevengel condensation/[1,7]-HT/cyclization/transesterification featuring novel structures and diastereoselective construction of all-carbon quaternary centers.

The use of alkyl amines and ethers as traceless hydride donors in [1,5]-hydride transfer cascade reactions represents a promising strategy that greatly enriches redox-neutral hydride transfer chemistry. This review summarizes the remarkable progress made in this field, and focuses on (1) alkyl amines as traceless hydride donors in cascade [1,5]-hydride transfer/elimination reactions and (2) alkyl ethers as traceless hydride donors in [1,5]-hydride transfer cascade reactions. The reaction mechanisms, features, scope, limitations, and synthetic applications are included, where appropriate. Importantly, its powerful ability in allene synthesis and the combination with [Re]-vinylidene and carbocation chemistries render this strategy attractive enough to inspire chemists to develop colorful reactions for building molecular complexity.

Medicinally significant 3-monosubstituted tetrahydroquinolines and 1,2-dihydroquinolines were controllably constructed via redox-neutral vinylogous cascade condensation/[1,5]-hydride transfer/cyclization in EtOH from readily available starting materials with alkenyl and coumarin moieties being introduced facilely, which have the features of green solvent, novel hydride acceptor, metal-free conditions, controllable syntheses of hydroquinoline derivatives and with water as the only by-product. In addition, the electrophilicity and nucleophilicity of α,α-dicyanoalkenes have been consecutively employed as hydride acceptors and γ-exclusive nucleophiles.

An efficient approach to achieve the divergent α-C(sp3)–H functionalization of cyclic amines through a rationally designed ring construction and ring deconstruction strategy was developed. A variety of spiro cyclohexadienone decorated cyclic amines were obtained via ring construction by molecular O2 oxidized dearomatization/cyclization. In addition, the sequential α-C(sp3)–H bond functionalization of cyclic amines was achieved via ring deconstruction through aromatization-driven C–C bond cleavage/intermolecular functionalization with the addition of diverse Grignard reagents or NaBD4.

The switchable synthesis of 3-non, 3-mono, 3,3'-disubstituted 3,4-dihydroquinolin-2(1H)-ones was developed through a redox-neutral hydride-transfer/N-dealkylation/N-acylation strategy from o-aminobenzaldehyde with 4-hydroxycoumarin, and Meldrum's acid, respectively. The unprecedented strategy for the synthesis of 3,3'-highly functionalized 3,4-dihydroquinolin-2(1H)-one has been realized with the in situ utilization of the released HCHO via the o-QM involved Michael addition. In addition, the synthetic utility of this protocol has been well illustrated via concise synthesis of CYP11B2 inhibitor.

The Grubbs–Hoveyda catalysts have a wide range of applications in catalyzed formation of the carbon-carbon double bonds. In this study, several imidazolium- functionalized or pyridinium-functionalized silver carboxylates have been prepared, and their reaction with Grubbs–Hoveyda 2nd generation (G–H 2nd) catalyst leads a new type of processes. Activity and selectivity of the catalysts have been preliminarily evaluated using cross olefin metathesis reactions.

Soil total nitrogen (STN) and the carbon/nitrogen ratio (C/N) influence both crop production and microbial activity, but their distributions under different tillage practices are not clearly unders...

The hydrogen-bonding-assisted construction of tetrahydroquinolines decorated with structurally diverse 3,3'-difunctional groups has been realized via a hydride transfer-involved three-step cascade reaction in the presence of morpholine. This protocol solves the limitation of acyclic 1,3-dicarbonyl compounds by one-pot synthesis of tetrahydroquinolines, featuring operational simplicity, broadly applicable substrates, and metal- and acid-free conditions with EtOH as a hydrogen-bonding donor.

The highly efficient construction of five and six membered heterocycle fused spirooxindoles was achieved via the [4 + 1] and formal [4 + 2] cycloaddition reactions between our rationally designed four-membered synthons and pyridinium methylides and α-bromoacetophenones, respectively. A wide range of richly decorated oxindole-containing chroman, chromen, and 2H-benzofuran derivatives were synthesized in moderate to high yields and diastereoselectivities.

The dual alkylation of the C(sp3)–H bond of cyclic α-methyl-N-sulfonyl imines has been achieved through the piperidine-promoted cascade condensation/[1,5]-hydride transfer/cyclization sequence from cyclic α-methyl-N-sulfonyl imines and o-aminobenzaldehydes in trifluoroethanol, providing structurally diverse 3-cyclic N-sulfonyl imine substituted tetrahydroquinolines in good yields with excellent diastereoselectivities.

Hydride transfer enabled the first success of the regioselective dearomatization of indoles in the carbocyclic ring and the pyrrole ring, which was induced by ortho-quinone methides and vinylogous iminium intermediates. A variety of spiro cyclohexaketenes featuring the dearomatized indoles and carbazoles as well as spiroindolenines were provided in moderate to high yields. The formidable challenge of switchable dearomatization of fused bicyclic aromatic compounds was addressed.

Aromatization-driven ring-opening/functionalization of common unstrained rings has been developed with the in situ generation of pre-aromatic fused spiro heterocycles as the key step, featuring (1) simple operation via a convenient one-pot reaction and (2) broad scope of various ring systems which do not require pre-activation.

A cerium-modified water hyacinth biochar adsorbent(Ce-BC) was developed through co-precipitation-pyrolysis to remove phosphate from wastewater. The study investigated the effects of Ce-BC dosing, wastewater pH, reaction time, and coexisting competing ions on the adsorption process. The results showed that the best adsorption performance was achieved with a maximum adsorption capacity of 35.00 mg·g

Herein, we report the first redox-neutral and transition-metal-free β-C(sp3)–H functionalization of cyclic amines via a consecutive intermolecular hydride transfer process. A series of N-aryl pyrro...

The pharmaceutically intriguing spiroindolenines incorporating tetrahydroquinoline were constructed via a hexafluoroisopropanol-promoted redox-neutral cascade cyclization from readily available starting materials. The benzazepinoindole skeletons could also be facilely accessed via one-pot sequential operation. Distinctive features of these transformations include their controllable access of the two privileged skeletons, high efficiency, simple operation, and mild reaction conditions.

The oxindole-embedded ortho-quinone methides were employed as reactive intermediates in formal [4 + 2] annulation with 1,3-dicarbonyls, providing an efficient access to spiro[chromen-4,3'-oxindole] scaffolds via a cascade conjugate addition/ketalization/dehydration process. This protocol featured metal-free conditions, wide substrate scope, and excellent yields.

Mitigating greenhouse gases (GHGs) emissions from rice paddy (Oryza sativa L.) and balancing the trade-offs between reducing emission and sustaining food security have raised global concerns. A global meta-analysis of rice experimental data was conducted to assess changes in emissions of GHGs (CH4 and N2O) and global warming potential (GWP) in response to improvements through 12 field management practices. The results indicated that changes in GWP were mainly attributed to CH4 emission even though N2O emission was significantly affected by conversion of field management practices. Specifically, GWP per unit rice plant area (area-scaled) was significantly increased by 20.1%, 66.2%, and 84.5% with nitrogen (N) fertilizer input, manuring, and residue retention (P

The aromatization-driven redox-neutral cascade [1,5]-hydride transfer/spirocyclization and cascade [1,5]-hydride transfer/hydrolysis from para-quinone methide in HFIP were developed. These protocols enabled the synthesis of azaspirocyclohexadienones and ortho-benzylated anilines in good to high yields under mild conditions, featuring room temperature, additive-free, and good functional group tolerance.

Impurity pinning has long been discussed to have a profound effect on the dynamics of an incommensurate charge density wave (CDW), which would otherwise slide through the lattice without resistance. Here we visualize the impurity pinning evolution of the CDW in ZrTe3 using the variable temperature scanning tunneling microscopy (STM). At low temperatures, we observe a quasi-1D incommensurate CDW modulation moderately correlated to the impurity positions, indicating a weak impurity pinning. As we raise the sample temperature, the CDW modulation gets progressively weakened and distorted, while the correlation with the impurities becomes stronger. Above the CDW transition temperature, short-range modulations persist with the phase almost all pinned by impurities. The evolution from weak to strong impurity pinning through the CDW transition can be understood as a result of losing phase rigidity.

Interface can be a fertile ground for exotic quantum states, including topological superconductivity, Majorana mode, fractal quantum Hall effect, unconventional superconductivity, Mott insulator, etc. Here we grow single-unit-cell (1UC) FeTe film on NbSe2 single crystal by molecular beam epitaxy (MBE) and investigate the film in-situ with home-made cryogenic scanning tunneling microscopy (STM) and non-contact atomic force microscopy (AFM) combined system. We find different stripe-like superlattice modulations on grown FeTe film with different misorientation angles with respect to NbSe2 substrate. We show that these stripe-like superlattice modulations can be understood as moire pattern forming between FeTe film and NbSe2 substrate. Our results indicate that the interface between FeTe and NbSe2 is atomically sharp. By STM-AFM combined measurement, we suggest the moire superlattice modulations have an electronic origin when the misorientation angle is relatively small (= 10 degree)., 10 pages, 4 figures

The switchable synthesis of 3-non, 3-mono, 3,3'-disubstituted 3,4-dihydroquinolin-2(1

Despite extensive characterization of sex differences in the medial preoptic area (mPOA) of the hypothalamus, we know surprisingly little about whether or how male and female mPOA neurons differ electrophysiologically, especially in terms of neuronal firing and behavioral pattern generation. In this study, by performing whole-cell patch clamp recordings of the mPOA, we investigated the influences of sex, cell type, and gonadal hormones on the electrophysiological properties of mPOA neurons. Notably, we uncovered significant sex differences in input resistance (male > female) and in the percentage of neurons that displayed post-inhibitory rebound (male > female). Furthermore, we found that the current mediated by the T-type Ca(2+) channel (I(T)), which is known to underlie post-inhibitory rebound, was indeed larger in male mPOA neurons. Thus, we have identified salient electrophysiological properties of mPOA neurons, namely I(T) and post-inhibitory rebound, that are male-biased and likely contribute to the sexually dimorphic display of behaviors. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s12264-020-00565-9) contains supplementary material, which is available to authorized users.

Climate change is a global issue threatening agricultural production and human survival. However, agriculture sector is a major source of global greenhouse gases (GHGs), especially CH4 and N2O. Crop residue returning (RR) is an efficient practice to sequestrate soil carbon and increase crop yields. However, the efficiency of RR to mitigate climate change and maintain food security will be affected by the response of GHG emissions at both per area-scale and per yield-scale. Therefore, a national meta-analysis was conducted using 309 comparisons from 44 publications to assess the responses of GHG emissions to RR in China's croplands. The results indicated that little response of GWP to RR was observed with conditions under lower nitrogen fertilizer input rates (0-120 kg ha-1), mulch retention, returning one time in double cropping systems, returning with half residue, weakly acidic soil (pH 5.5-6.5), initial SOC contents >20 g kg-1, or mean annual precipitation

Here, we designed a double-solvent/host-guest redox combined strategy to construct Cu+ sites in metal-organic frameworks (MOFs) for the first time. As a proof of concept, a representative MOF MIL-100(Fe) with tunable valence states of cations was employed as the host. The combined strategy realizes selective introduction of Cu2+ precursors to the interior pores of MIL-100(Fe), remarkably minimizing the aggregation of Cu2+ and subsequently formed Cu+ species. Owing to the proper reducibility of in situ formed Fe2+ in the frameworks, controlled conversation of Cu2+ to Cu+ with ∼100% yield is achieved in the absence of any additional reducing agents. These characteristics make the obtained materials Cu+-modified MIL-100(Fe) highly active in selective CO adsorption. The CO adsorption capacity is up to 3.75 mmol·g-1 at 298 K and 1 bar, which is superior to all other Cu+-containing adsorbents reported so far such as CuCl/activated carbon (2.5 mmol·g-1), CuCl/γ-Al2O3 (1.0 mmol·g-1), and CuCl/SBA-15 (0.50 mmol·g-1). The same adsorbent also exhibits quite high selectivity of CO over N2, and the ideal adsorption solution theory selectivity reaches 424. The outstanding CO adsorption performance make the present adsorbents great potential in separation of CO from various mixtures.

A novel hydride transfer initiated ring expansion of 4-pyrrolidinyl isatins to synthesize tetrahydro-1-benzazepines has been developed. This methodology represents an atom- and step-economical protocol to assemble seven-membered polycyclic amines from pyrrolidine derivatives in one step.

The medial preoptic area (mPOA) differs between males and females in nearly all species examined to date, including humans. Here, using fiber photometry recordings of Ca2+ transients in freely behaving mice, we show ramping activities in the mPOA that precede and correlate with sexually dimorphic display of male-typical mounting and female-typical pup retrieval. Strikingly, optogenetic stimulation of the mPOA elicits similar display of mounting and pup retrieval in both males and females. Furthermore, by means of recording, ablation, optogenetic activation, and inhibition, we show mPOA neurons expressing estrogen receptor alpha (Esr1) are essential for the sexually biased display of these behaviors. Together, these results underscore the shared layout of the brain that can mediate sex-specific behaviors in both male and female mice and provide an important functional frame to decode neural mechanisms governing sexually dimorphic behaviors in the future., The medial preoptic area (mPOA) in a mammalian brain is sexually dimorphic, and yet its exact function in mediating gender-specific behavior remains unclear. Here, Xu and colleagues show that optogenetic manipulation of the mPOA in male mice induce female-stereotyped behaviors and vice versa.

Aromatization as the driving force to initiate hydride transfer addressed the drawbacks of hydride transfer-involved reactions., An unprecedented cascade dearomative cyclization through hydrogen-bonding-assisted hydride transfer is realized. The aggregate effect of HFIP enables the rapid buildup of polycyclic amines directly from phenols and o-aminobenzaldehydes via a cascade dearomatization/rearomatization/dearomatization sequence. This unique transformation addressed the drawbacks of hydride transfer-involved redox-neutral reactions.

Cu(I)-containing materials have great potential in various applications such as in CO adsorption; however, development of an efficient and controllable method to produce Cu(I) sites remains a significant challenge; herein, a two-step double-solvent (DS) strategy is reported for the first time to fabricate Cu(I) sites in a representative metal–organic framework, MIL-101(Cr); this strategy ensures that both introduction of the Cu(II) precursor and its reduction to Cu(I) occur inside the pores and significantly minimizes the aggregation of Cu species. This is difficult to realize through conventional methods used for Cu(II) introduction (wet impregnation) or reduction (liquid-phase reduction). The two-step DS strategy involves selective reduction of Cu(II) to form Cu(I) without the formation of any Cu(0). The obtained Cu(I)-containing materials exhibit an excellent CO adsorption capacity (up to 2.42 mmol g−1) at 298 K and 1 bar, much better than that of the benchmark adsorbents including CuCl/γ-Al2O3 (1.0 mmol g−1), CuCl/MCM-41 (0.57 mmol g−1), and CuZSM-5 (0.11 mmol g−1).

Carbocation-initiated cascade [1,5]-hydride transfer/cyclization and dimerization reactions were developed to synthesize dihydrodibenzo[b,e]azepine and octahydrodipyrroloquinoline derivatives in high yields. These redox-neutral C(sp3)-H functionalization-involving cascade reactions feature transition-metal-free, high atom- and step-economy, and environmental friendliness with water as the sole byproduct.

The organocatalytic alkylation of 2-methyl-N-heteroaromatics with alcohols has been achieved via SN1-type C(sp3)–H functionalization, providing a green and efficient synthesis of indole and ferrocene-functionalized N-heteroaromatics in high yields.

The first transition-metal free and regioselective C(sp3)-H arylation of 2-alkylazaarenes with nitroarenes has been achieved via t-BuOK-mediated dehydrogenative C(sp3)-C(sp2) coupling. This reaction provides an efficient access to the biologically important and synthetically useful 2-benzyl-substituted azaarenes under mild conditions without the need of prefunctionalization of 2-alkylazaarenes or using the specialized arylating agents.