Enantioconvergent Cu-catalysed N-alkylation of aliphatic amines.

Chiral amines are commonly used in the pharmaceutical and agrochemical industries1. The strong demand for unnatural chiral amines has driven the development of catalytic asymmetric methods1,2. Although the N-alkylation of aliphatic amines with alkyl halides has been widely adopted for over 100 years, catalyst poisoning and unfettered reactivity have been preventing the development of a catalyst-controlled enantioselective version3-5. Here we report the use of chiral tridentate anionic ligands to enable the copper-catalysed chemoselective and enantioconvergent N-alkylation of aliphatic amines with α-carbonyl alkyl chlorides. This method can directly convert feedstock chemicals, including ammonia and pharmaceutically relevant amines, into unnatural chiral α-amino amides under mild and robust conditions. Excellent enantioselectivity and functional-group tolerance were observed. The power of the method is demonstrated in a number of complex settings, including late-stage functionalization and in the expedited synthesis of diverse amine drug molecules. The current method indicates that multidentate anionic ligands are a general solution for overcoming transition-metal-catalyst poisoning.

In Situ Electrochemical Rapid Induction of Highly Active γ-NiOOH Species for Industrial Anion Exchange Membrane Water Electrolyzer.

Limited by the strong oxidation environment and sluggish reconstruction process in oxygen evolution reaction (OER), designing rapid self-reconstruction with high activity and stability electrocatalysts is crucial to promoting anion exchange membrane (AEM) water electrolyzer. Herein, trace Fe/S-modified Ni oxyhydroxide (Fe/S-NiOOH/NF) nanowires are constructed via a simple in situ electrochemical oxidation strategy based on precipitation-dissolution equilibrium. In situ characterization techniques reveal that the successful introduction of Fe and S leads to lattice disorder and boosts favorable hydroxyl capture, accelerating the formation of highly active γ-NiOOH. The Density Functional Theory (DFT) calculations have also verified that the incorporation of Fe and S optimizes the electrons redistribution and the d-band center, decreasing the energy barrier of the rate-determining step (*O→*OOH). Benefited from the unique electronic structure and intermediate adsorption, the Fe/S-NiOOH/NF catalyst only requires the overpotential of 345 mV to reach the industrial current density of 1000 mA cm-2 for 120 h. Meanwhile, assembled AEM water electrolyzer (Fe/S-NiOOH//Pt/C-60 °C) can deliver 1000 mA cm-2 at a cell voltage of 2.24 V, operating at the average energy efficiency of 71% for 100 h. In summary, this work presents a rapid self-reconstruction strategy for high-performance AEM electrocatalysts for future hydrogen economy.

Copper-Catalyzed Enantioconvergent Radical C(sp3)-N Cross-Coupling of Activated Racemic Alkyl Halides with (Hetero)aromatic Amines under Ambient Conditions.

The enantioconvergent C(sp3)-N cross-coupling of racemic alkyl halides with (hetero)aromatic amines represents an ideal means to afford enantioenriched N-alkyl (hetero)aromatic amines yet has remained unexplored due to the catalyst poisoning specifically for strong-coordinating heteroaromatic amines. Here, we demonstrate a copper-catalyzed enantioconvergent radical C(sp3)-N cross-coupling of activated racemic alkyl halides with (hetero)aromatic amines under ambient conditions. The key to success is the judicious selection of appropriate multidentate anionic ligands through readily fine-tuning both electronic and steric properties for the formation of a stable and rigid chelating Cu complex. Thus, this kind of ligand could not only enhance the reducing capability of a copper catalyst to provide an enantioconvergent radical pathway but also avoid the coordination with other coordinating heteroatoms, thereby overcoming catalyst poisoning and/or chiral ligand displacement. This protocol covers a wide range of coupling partners (89 examples for activated racemic secondary/tertiary alkyl bromides/chlorides and (hetero)aromatic amines) with high functional group compatibility. When allied with follow-up transformations, it provides a highly flexible platform to access synthetically useful enantioenriched amine building blocks.

Synthesis of α-Quaternary ß-Lactams via Copper-Catalyzed Enantioconvergent Radical C(sp3 )-C(sp2 ) Cross-Coupling with Organoboronate Esters.

The copper-catalyzed enantioconvergent radical C(sp3 )-C(sp2 ) cross-coupling of tertiary α-bromo-ß-lactams with organoboronate esters could provide the synthetically valuable α-quaternary ß-lactams. The challenge arises mainly from the construction of sterically congested quaternary stereocenters between the tertiary alkyl radicals and chiral copper(II) species. Herein, we describe our success in achieving such transformations through the utilization of a copper/hemilabile N,N,N-ligand catalyst to forge the sterically congested chiral C(sp3 )-C(sp2 ) bond via a single-electron reduction/transmetalation/bond formation catalytic cycle. The synthetic potential of this approach is shown in the straightforward conversion of the corresponding products into many valuable building blocks. We hope that the developed catalytic cycle would open up new vistas for more enantioconvergent cross-coupling reactions.

Reliability of computed molecular structures.

When the structures of 1342 molecules are optimized by 30 methods and 7 basis sets, there appear 289 (21.54%) problematic molecules and 112 (8.35%) failed ones. When 278 problematic molecules are compared, the best methods are BHandH and LC-wPBE, while B97D, BP86, HFS, VSXC, and HCTH are very unreliable. When 179 problematic molecules are computed with larger basis sets, the smallest mean absolute deviation (MAD) of bond angle (2.3°) is shown by QCISD(T)/cc-pVTZ, while the smallest MAD of bond length (0.021 Å), the best SUM1 (4.9 unit), and the best SUM2 (2.4 unit) are shown by DSDPBEP86(Full), DSDPBEP86, PBE1PBE-D3, MP2, and MP2(Full) in combination with aug-cc-pVQZ, cc-pVQZ, Def2QZVP, Def2TZVPP, and/or 6-311++G(3df,3pd). Very large basis sets, for example, larger than cc-pVTZ usually have to be used to obtain very good structures and the performances of many density-functional theory methods are encouraging. The best results may be the limit of modern computational chemistry.

Enantioconvergent Cu-Catalyzed Radical C-N Coupling of Racemic Secondary Alkyl Halides to Access α-Chiral Primary Amines.

α-Chiral alkyl primary amines are virtually universal synthetic precursors for all other α-chiral N-containing compounds ubiquitous in biological, pharmaceutical, and material sciences. The enantioselective amination of common alkyl halides with ammonia is appealing for potential rapid access to α-chiral primary amines, but has hitherto remained rare due to the multifaceted difficulties in using ammonia and the underdeveloped C(sp3)-N coupling. Here we demonstrate sulfoximines as excellent ammonia surrogates for enantioconvergent radical C-N coupling with diverse racemic secondary alkyl halides (>60 examples) by copper catalysis under mild thermal conditions. The reaction efficiently provides highly enantioenriched N-alkyl sulfoximines (up to 99% yield and >99% ee) featuring secondary benzyl, propargyl, α-carbonyl alkyl, and α-cyano alkyl stereocenters. In addition, we have converted the masked α-chiral primary amines thus obtained to various synthetic building blocks, ligands, and drugs possessing α-chiral N-functionalities, such as carbamate, carboxylamide, secondary and tertiary amine, and oxazoline, with commonly seen α-substitution patterns. These results shine light on the potential of enantioconvergent radical cross-coupling as a general chiral carbon-heteroatom formation strategy.

Numerical simulation of all-optical logic gates based on hybrid-cavity semiconductor lasers.

All-optical switch and multiple logic gates have been demonstrated using a hybrid-cavity semiconductor laser composed of a square microcavity and a Fabry-Perot cavity experimentally. In this paper, two-section tri-mode rate equations with optical injection terms are proposed and applied to study all-optical logic gates of NOT, NOR, and NAND operations utilizing the hybrid-cavity laser. Steady-state and dynamical characteristics of all-optical multiple logic gates are simulated, taking into account the influence of mode frequency detuning, gain suppression coefficients, mode Q factor, injection energy, and biasing current. All-optical logic NOT, NOR, and NAND gates up to 20, 15, and 20 Gbit/s are obtained numerically with dynamic extinction ratios of over 20, 20, and 10 dB, respectively, which are potential response speeds of the all-optical logic gates based on the hybrid-cavity semiconductor lasers.

Copper-Catalyzed Enantioconvergent Cross-Coupling of Racemic Alkyl Bromides with Azole C(sp2 )-H Bonds.

The development of enantioconvergent cross-coupling of racemic alkyl halides directly with heteroarene C(sp2 )-H bonds has been impeded by the use of a base at elevated temperature that leads to racemization. We herein report a copper(I)/cinchona-alkaloid-derived N,N,P-ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2 )-H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α-chiral alkylated azoles, such as 1,3,4-oxadiazoles, oxazoles, and benzo[d]oxazoles as well as 1,3,4-triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2 )-H bond and the involvement of alkyl radical species under the reaction conditions.

Copper-Catalyzed Asymmetric Radical 1,2-Carboalkynylation of Alkenes with Alkyl Halides and Terminal Alkynes.

A copper-catalyzed intermolecular three-component asymmetric radical 1,2-carboalkynylation of alkenes has been developed, providing straightforward access to diverse chiral alkynes from readily available alkyl halides and terminal alkynes. The utilization of a cinchona alkaloid-derived multidentate N,N,P-ligand is crucial for the efficient radical generation from mildly oxidative precursors by copper and the effective inhibition of the undesired Glaser coupling side reaction. The substrate scope is broad, covering (hetero)aryl-, alkynyl-, and aminocarbonyl-substituted alkenes, (hetero)aryl and alkyl as well as silyl alkynes, and tertiary to primary alkyl radical precursors with excellent functional group compatibility. Facile transformations of the obtained chiral alkynes have also been demonstrated, highlighting the excellent complementarity of this protocol to direct 1,2-dicarbofunctionalization reactions with C(sp2/sp3)-based reagents.

Wideband frequency-tunable optoelectronic oscillator with a directly modulated AlGaInAs/InP integrated twin-square microlaser.

We propose and demonstrate an optoelectronic oscillator with a directly modulated AlGaInAs/InP integrated twin-square microlaser for generating wideband frequency-tunable microwave signals with low phase noise. Apart from the relaxation oscillation peak, the modulation response of the twin-square microlaser working at the mutual optical injection state exhibits a significant enhancement around the beating frequency of the lasing modes in the two square cavities owing to the photon-photon resonance. A self-sustaining oscillation can be generated around the modulation response peak with the lowest loop loss occurring at the relaxation oscillation frequency or the beating frequency, depending on the practical state of the twin-square microlaser. High-quality tunable microwave signals ranging from 2.22 to 19.52 GHz are generated with single sideband phase noises below -110 dBc/Hz at the 10 kHz offset frequency and side-mode suppression ratios of approximately 40 dB by tuning the injection currents of the twin-square microlaser.

Low-phase-noise microwave generation using dual-mode microsquare laser phase locking by modulated sidebands.

An effective method for millimeter-wave (mmW) carrier generation from a dual-transverse-mode microsquare laser is experimentally demonstrated. By directly modulating the dual-mode microsquare laser at 6.7 GHz, multiple sidebands are generated due to enhanced modulation nonlinearity, and the lasing modes with an interval of 40 GHz are phase-locked. MmW carriers up to 47 GHz, corresponding to seven times that of the modulation frequency, are achieved with a linewidth below 10 Hz. The single-sideband phase noises of the signals keep the same level after transmission over 2.5 km of optical fiber.

Single-transverse-mode waveguide-coupled deformed hexagonal resonator microlasers.

AlGaInAs/InP waveguide-coupled deformed hexagonal resonator microlasers with enhanced mode quality (Q)-factors are demonstrated for realizing single-transverse-mode operation. A circular hole is introduced to the center of the hexagonal resonators with rounded corners to enhance the mode Q-factors and suppress high-order transverse modes simultaneously. Single-mode lasing with side-mode suppression ratios up to 40 dB is obtained for the 10-µm-sidelength hexagonal microlasers with a center hole. All the lasing spectra demonstrate pure single-transverse-mode properties within the whole tuning range of injection current, and mode hopping with one, two, and three longitudinal-mode intervals is observed due to the mode Q-factor modification by the center holes. To further reduce the device size and threshold current, the deformed hexagonal resonator microlasers with the flat sides replaced by circular arcs are analyzed and demonstrated experimentally. The Q-factors of the fundamental transverse modes can be enhanced by two orders of magnitude due to the convergence effect of the circular sides by optimizing the deformation amplitude, while the single-transverse-mode property is still maintained. A threshold current of 2.4 mA is realized for a circular-side hexagonal microlaser with the side length of 8.5 µm and the deformation amplitude of 0.55 µm.

All-optical flip-flop based on hybrid square-rectangular bistable lasers.

A compact, simple, and bistable hybrid square-rectangular laser is experimentally demonstrated as an all-optical flip-flop memory. Controllable bistability is induced by two-mode competition, together with the saturable absorption at the square microcavity section. The all-optical set and reset operations are realized by injecting signal pulses at two-mode wavelengths, with the response times of 165 and 60 ps at the triggering pulse width of 100 ps and switching energies of 2.7 and 14.2 fJ, respectively. The robust hybrid-cavity design has an active area of 660 µm2 and permits efficient unidirectional single-mode lasing, low-power flip-flop operation, and superior fabrication tolerance for monolithic photonic integration.

Multicoherence wavelength generation based on integrated twin-microdisk lasers.

An effective method for multicoherence wavelength generation is experimentally demonstrated using an integrated twin-microdisk laser as a seeding source. Dual-wavelength lasing with variable wavelength spacing is achieved by adjusting injection currents independently. Using the integrated laser as a pump seed, we obtain multicoherence wavelength in a nonlinear optical fiber, which has a tunable frequency interval from 50 to 300 GHz. Ten waves with optical signal to noise ratio from 28 to 10 dB are produced at the frequency interval of 200 GHz and a pulse width of 1.2 ps. The high extinction ratio of the pulse trace indicates the high coherence in the mode-locked multiwavelength light source.

Evaluating the expression of CARMA3 as a prognostic tumor marker in renal cell carcinoma.

Increased expression of CARMA3 has been reported to be involved in tumorigenesis and tumor progression of several cancer types. The aim of our study is to investigate the prognostic role of CARMA3 expression in patients with renal cell carcinoma (RCC). Real-time quantitative PCR was performed to detect CARMA3 mRNA expression level in 31 paired samples of RCC and adjacent noncancerous renal tissues. Subsequently, extensive immunohistochemistry was performed to detect CARMA3 protein expression in 114 RCC cases. Clinicopathological data for these patients were evaluated. The prognostic significance was assessed using the Kaplan-Meier survival estimates and log-rank tests. CARMA3 mRNA expression was significantly higher in RCC tissues compared with adjacent noncancerous renal tissues (3.525 ± 1.233 vs. 1.512 ± 0.784, P < 0.001). In addition, high CARMA3 expression in RCC tissues was significantly associated with tumor size (P = 0.026), histological differentiation (P = 0.039), tumor stage (P = 0.006), and the presence of metastasis (P < 0.001). Moreover, Kaplan-Meier analysis showed that patients with high CARMA3 expression also had a significantly poorer prognosis than those with low CARMA3 expression (log-rank test, P < 0.001). Furthermore, multivariate analysis illustrated that CARMA3 overexpression might be an independent prognostic indicator for the survival of patients with RCC. In conclusion, this work shows that CARMA3 may serve as a novel and prognostic marker for RCC and play a role during the development and progression of the disease.

Fe-doping and oxygen vacancy achieved by electrochemical activation and precipitation/dissolution equilibrium in NiOOH for oxygen evolution reaction.

The poor conductivities and instabilities of accessible nickel oxyhydroxides hinder their use as oxygen evolution reaction (OER) electrocatalysts. Herein, we constructed Fe-NiOOH-OV-600, an Fe-doped nickel oxide hydroxide with abundant oxygen vacancies supported on nickel foam (NF), using a hydrothermal method and an electrochemical activation strategy involving 600 cycles of cyclic voltammetry, assisted by the precipitation/dissolution equilibrium of ferrous sulfide (FeS) in the electrolyte. This two-step method endows the catalyst with abundant Fe-containing active sites while maintaining the ordered structure of nickel oxide hydroxide (NiOOH). Characterization and density functional theory (DFT) calculations revealed that synergy between trace amounts of the Fe dopant and the oxygen vacancies not only promotes the generation of reconstructed active layers but also optimizes the electronic structure and adsorption capacity of the active sites. Consequently, the as-prepared Fe-NiOOH-OV-600 delivered large current densities of 100 and 1000 mA cm-2 for the OER at overpotentials of only 253 and 333 mV in 1 mol/L KOH. Moreover, the catalyst is stable for at least 100 h at 500 mA cm-2. This work provides insight into the design of efficient transition-metal-based electrocatalysts for the OER.

Directed electron regulation promoted sandwich-like CoO@FeBTC/NF with p-n heterojunctions by gel electrodeposition for oxygen evolution reaction.

Metal organic framework (MOF) is currently-one of the key catalysts for oxygen evolution reaction (OER), but its catalytic performance is severely limited by electronic configuration. In this study, cobalt oxide (CoO) on nickel foam (NF) was first prepared, which then wrapped it with FeBTC synthesized by ligating isophthalic acid (BTC) with iron ions by electrodeposition to obtain CoO@FeBTC/NF p-n heterojunction structure. The catalyst requires only 255 mV overpotential to reach a current density of 100 mA cm-2, and can maintain 100 h long time stability at 500 mA cm-2 high current density. The catalytic properties are mainly related to the strong induced modulation of electrons in FeBTC by holes in the p-type CoO, which results in stronger bonding and faster electron transfer between FeBTC and hydroxide. At the same time, the uncoordinated BTC at the solid-liquid interface ionizes acidic radicals which form hydrogen bonds with the hydroxyl radicals in solution, capturing them onto the catalyst surface for the catalytic reaction. In addition, CoO@FeBTC/NF also has strong application prospects in alkaline electrolyzers, which only needs 1.78 V to reach a current density of 1 A cm-2, and it can maintain long-term stability for 12 h at this current. This study provides a new convenient and efficient approach for the control design of the electronic structure of MOF, leading to a more efficient electrocatalytic process.

Mechanism-based ligand design for copper-catalysed enantioconvergent C(sp3)-C(sp) cross-coupling of tertiary electrophiles with alkynes.

In contrast with the well-established enantioconvergent radical C(sp3)-C cross-coupling of racemic secondary alkyl electrophiles, the corresponding coupling of tertiary electrophiles to forge all-carbon quaternary stereocentres remains underexplored. The major challenge arises from the steric hindrance and the difficult enantio-differentiation of three distinct carbon substituents of prochiral tertiary radicals. Here we demonstrate a general copper-catalysed enantioconvergent C(sp3)-C(sp) cross-coupling of diverse racemic tertiary alkyl halides with terminal alkynes (87 examples). Key to the success is the rational design of chiral anionic N,N,N-ligands tailor-made for the computationally predicted outer-sphere radical group transfer pathway. This protocol provides a practical platform for the construction of chiral C(sp3)-C(sp/sp2/sp3) bonds, allowing for expedient access to an array of synthetically challenging quaternary carbon building blocks of interest in organic synthesis and related areas.

[Parallel factor analysis for excitation emission matrix fluorescence spectroscopy of dissolved organic matter from a reservoir-type river].

The fluorescent components and their distribution and variation of dissolved organic matter (DOM) were examined using excitation emission matrix fluorescence spectroscopy-parallel factor analysis technique (EEMs-PARAFAC) for samples collected during June, 2008 from Minjiang River, a typical subtropical reservoir-type river ecosystem. Three separate fluorescent components were identified by PARAFAC, including two dominant humic-like components (C1: < 250, 325/424 nm; C2: 270, 395/482 nm) and one protein-like component (C3: < 250, 280/358 nm), of which humic-like components were dominant. Fluorescence analysis provided a 'fingerprint' technique to trace the mixing of DOM between three tributaries in the upstream of Minjiang River. The nearly constant concentration and composition in the main stream of Minjiang River reflected the effect of dam construction Correlation and principal component analysis (PCA) revealed that humic-like components were principally derived from flushing of watershed soils, while protein-like component was formed from in-situ production which could be used as a proxy of the concentration of total dissolved nitrogen (TDN). Multi-linear regression of fluorescent components C2 and C3 can be used to trace the variation of dissolved organic carbon (DOC) concentration. This study demonstrates that Minjiang is a typical subtropical reservoir-type river which still keeps relatively 'unpolluted' aquatic environment.

Promoting Oxygen Evolution by Deep Reconstruction via Dynamic Migration of Fluorine Anions.

Promoting the reconstruction of electrocatalysts during the oxygen evolution reaction (OER) is generally regarded as a promising strategy for enhanced activity. F anions with strong electronegativity are predicted to enhance this transformation. Herein, a fluorine-anion doping route is proposed to convert the well-latticed NiMoO4@MNF to amorphous F-NiMoO4@MNF by a facile and versatile molten salt strategy. The well-defined nanorod arrays guarantee abundant exposed active sites, rapid mass transfer, and fast gas bubble release. Moreover, the emerged loose amorphous structure is conducive to the dynamic migration of F species and effective penetration of the electrolyte; therefore, the resulting exchange between F and hydroxide anions induces the formation of an active oxy(hydroxide) layer, thus finally optimizing the electronic structure and absorption/desorption energy on the surface of F-NiMoO4@MNF. The boosted OER performance of reconstructed F-NiMoO4@MNF is reliably confirmed by a low overpotential of 188 mV at 50 mA cm-2, a small Tafel slope of 33.8 mV dec-1, and favorable long-term stability. In addition, accelerated hydrogen evolution is observed, which is ascribed to the finely tuned electron distribution. This work would provide a new reconstruction route assisted by F-anion doping to the development of high-performance catalysts.