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The 3d transition metal-catalyzed enantioconvergent radical cross-coupling provides a powerful tool for chiral molecule synthesis. In the classic mechanism, the bond formation relies on the interaction between nucleophile-sequestered metal complexes and radicals, limiting the nucleophile scope to sterically uncongested ones. The coupling of sterically congested nucleophiles poses a significant challenge due to difficulties in transmetalation, restricting the reaction generality. Here, we describe a probable outer-sphere nucleophilic attack mechanism that circumvents the challenging transmetalation associated with sterically congested nucleophiles. This strategy enables a general copper-catalyzed enantioconvergent radical N-alkylation of aromatic amines with secondary/tertiary alkyl halides and exhibits catalyst-controlled stereoselectivity. It accommodates diverse aromatic amines, especially bulky secondary and primary ones to deliver value-added chiral amines (>110 examples). It is expected to inspire the coupling of more nucleophiles, particularly challenging sterically congested ones, and accelerate reaction generality.

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.

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.

Epimedii Foliumis the most important osteogenic herb formulated for the traditional Chinese Medicine Xian Ling Gu Bao (XLGB) capsule. The present study compared XLGB capsules containing two different Epimediumspecies, i.e., either Epimedium pubescens(XEP) or Epimedium koreanum(XEK), with the focus being on the chemical constituents and antiosteoporotic efficacy.

Using ANSYS finite element analysis software, the crushing effect and wall rock deformation of a small high-pressure jet impacting coal were given numerical simulation analysis. It verified that impacting increased exposed area of coal in punch, providing conditions for pressure relief of internal coal seam and gas seepage. through comprehensive analysis of the rock stress and coal displacement of different roadway models after undercutting, it was determined that aperture size was 4/15 or so of roadway floor length, thus roadway fissures developed full, and maintained rock integrity, in favor of speeding up the face driving.

Through ANSYS/LS-DYNA simulates mini-jet fracturing coal effect, this paper verifies that high-pressure mini-jet forms ahead hole on working face coal, which increases coal exposing area and relieves pressure inside the coal bed to creative conditions for gas relieving and flowing. Additionally underground stress, the coal around hole shifts to the hole space and enlarges the hole relieving pressure and gas exhausting scope further, which removes the coal outburst potential within the control scope and provides theoretical basis for studing the equipment of high-pressure mini-jet cutting hole against outburst.

Soft rock roadway is one challenge of roadway support. With plastic state, it has a certain bearing strength, and its large plastic performance must release out in some form. Therefore soft rock roadway is not a single support effective, it must use a joint way. By numerical simulation, this paper analyzes uniform diffusion of bolt mesh support to wall rock stress, which provides a theoretical basis for bolt mesh support of soft rock.

Through the synthetically analysis of the characteristics of coal mining and the environment quality of the mining area, the environment quality evaluation index system is formed: water and soil environment quality are the principal layer, the influence factors are measure layer. The evaluation degree of every factor is defined by fuzzy synthesis evaluation method and the environment quality level and the problem urgently to result are found, which provides theory support for environmental protection and green development.

As impacting and cutting role of the small jet, coal around slots occured violent displacement and expansion, increasing coal cracks, which greatly improved gas flow in coal seams and made for gas emission. The original coal stress changed and stress concentration belt moved to coal seams depth constantly. With gradual relief expansion and fracture increased, coal seam permeability coefficient increased, gas pressure decreased. Coal potentiality released, coal crushed and moved, a lot of gas with adsorption state changed free, then gas fully released and gas pressure gradient decreased, which reduced outstanding risk. it was determined that aperture size was 4/15 or so of roadway floor length using ANSYS finite element analysis software, thus roadway fissures developed full, and maintained rock integrity, in favor of speeding up the face driving.

Fire hazard is one of the severe casualty accident, which injures the life-safety of the miner crucially and disturbs the sustained development of the coal mine. Recently the check-up table is the mere method applying for the assessment of the fire hazard, and the assessment conclusion is subjective intensively and the Index System of the Safety Assessment is not perfect, because the dangerous degree of fire hazard is set up by the professional. In this paper, the seven factors were generalized through the statistic and analysis of the 56 fire hazards, which included self-ignite gradation of coal bed, miner stuff, management of ventilation of coal pits, fire control system, safety administration, mine combustible, risk ratio of the electrical equipment. The ratio of each factor was confirmed by the method of layered analysis, the safety degree was set up through data processing and the proper measure and suggestion were put forward according to the safety result.

Through the synthetically analysis of the composite index method for evaluation of rock burst rating, the limitation of this method is discussed. Mines have various burst development characteristics, and geological condition and mining technical factors decide different rock burst weights greatly. So this paper prefers an optimal case based on analytic hierarchy process, using cooperation matrix to decide the influence weight of the factors on the burst, and synthetized with the actual impact risk index, which makes the method more precise and objective to evaluate the burst rating to provide a scientific basis for safe investment of the mine.

With the development of technology and the society, the demand standard of enterprise to talented person is more and more strict. Through analyzing the special function of some methods, such as to carry out tutorial system, to reform teaching methods, to strengthen teaching management, to improve engineering test methods and improve school infrastructure measures, this paper discusses the new method to cultivate high quality engineering and technical personnel to provid theoretical guidance for future universities to meet market demand and cultivate innovative talents.

The entire mitochondrial genome of the bristletail Pedetontus silvestrii (Mendes) (Archaeognatha: Machilidae) was sequenced. The genome is 15,879 bp and bears the standard set of genes common to all arthropods. Genome features like nucleotide composition and codon use are compared with three other bristletails. The gene trnQ was inverted compared with the order in other hexapods. The major noncoding region (the A+T-rich region or control region) between the small ribosomal subunit (rrnS) and the trnI gene includes one extensive repeat region, which has two tandem repeats of a 128-bp sequence. A+T content is higher than in other known species of Archaeognatha and Zygentoma but is similar to that in Collembola and Pterygota.