Chiral transfer: the fluorinated sulfoximine (see scheme; Ts=p-toluenesulfonyl) was synthesized and used as the first chiral fluoromethylenation reagent for the synthesis of cyclopropanes that ...contain fluorinated tertiary stereogenic carbon centers in good yields, good diastereoselectivity, and excellent enantioselectivity.
Abstract
The large-scale volume fracturing development of shale oil horizontal wells, and the production is affected by seasonal cycle and emergencies, resulting in the complexity of production ...prediction. Aiming at the problem of poor actual effect or heavy workload of shale oil production prediction by classical reservoir engineering, reservoir numerical simulation and other methods, a new shale oil production prediction method based on Prophet algorithm is proposed It is easier to find the inherent law from a small amount of data. In this paper, we use the production data of production wells in Huanjiang A reservoir in 2015 to predict the production, and compare the prediction results with long-term and short-term memory neural network (LSTM) and ARPS production decline model. The results show that the prediction accuracy of Prophet algorithm is higher, and it is more accurate for the production of complex shale oil.
Herein, we report the discovery of the catalytic asymmetric conjugated addition of allylstannanes to indol-2-ones promoted by Ni(II)/chiral N,N′-dioxide. This method enables the stereodivergent ...construction of contiguous quaternary carbon centers (CQCCs), which can be readily achieved by a suitable combination of a chiral catalyst with stereospecific allylstannanes. This protocol allows for a unified access to all stereoisomers of 3,3-disubstituted oxindoles with CQCCs in good to excellent enantioselectivities and diastereoselectivities.
The Chang 7 oil group in the Ordos Basin has the characteristics of a tight lithology, a low formation pressure coefficient and strong reservoir heterogeneity. To better determine reasonable ...developmental technical countermeasures, oiliness, seepage capacity, and compressibility evaluations are combined. Using a combination of field practice and laboratory experiments, six types of sweetness classification evaluation parameters are screened: oil saturation, longitudinal oil layer structure coefficient, average pore throat radius, gas-oil ratio, brittleness index, and minimum horizontal principal stress. By combining the relationships among variables with the initial production from directional wells, the gray correlation method is used to quantify the weights of the contributions of evaluation parameters to production. On this basis, using the difference method for the curve slope, a sweetness evaluation and classification method for the Chang 7 oil group is constructed, and it solves the difficult problem of quality difference classification for the Chang 7 oil group and provides a reference basis for the optimal design of well patterns and fracturing reconstruction parameters.
This work features first asymmetric Ni-catalyzed reductive coupling of allylic carbonates with aldehydes, which may proceed via allyl-Ni intermediates although Zn was used as the terminal reductant. ...Moderate to excellent enantiomeric excess was obtained with excellent functional group tolerance.
A normal phase high performance liquid chromatographic method was established for the simultaneous determination of tanshinones in Salvia miltiorrhiza Bunge. Tanshinones, including cryptotanshinone, ...tanshinone I, and tanshinone IIA were successfully separated on a silica column using the mixture of n-hexane and dichloromethane (96/4, v/v) as mobile phase. The results of the quantitative experiments proved that methanol is the best solvent in the five common solvents. Linear equations revealed good linear relationship between the peak areas of tanshinones and their concentrations. The effect of the dipping time and ultrasonic time were measured, the trend lines dependent on the linear equations were drawn, and the ultrasonic condition was better than the dipping condition.
Molecules containing a difluoromethyl group or a propargylic stereocenter are widely used in pharmaceuticals and agrochemicals, and 1,2‐functionalization of olefins is an important method for ...introducing the two groups into molecules simultaneously. The construction of the propargylic stereocenter with terminal alkynes usually requires bases. However, difluoromethylating agents with high reduction potentials often decompose in the presence of bases because of their acidities, and those with low reduction potentials are stable but difficult to undergo the desired single electron transfer (SET) reduction. Using the linear relationship between reduction potential differences (ΔE) and Hammett substituent constants (σ) of difluoromethyl aryl sulfones, we solved the dilemma between acidities and reduction potentials of difluoromethylating agents. Herein, we report the first enantioselective difluoromethylation‐alkynylation of olefins with difluoromethyl 4‐chlorophenyl sulfone with high enantioselectivity (>90 % ee). We also extended this asymmetric fluoroalkylation‐alkynylation reaction with other fluoroalkyl sulfones, which enabled efficient installation of trifluoromethyl, difluoroalkyl, difluorobenzyl, (benzenesulfonyl)‐difluoromethyl and monofluoromethyl groups into products.
The linear relationship between reduction potential differences (ΔE) and substituent constants (σ) of aryl difluoromethyl sulfones provides a powerful strategy to solve the dilemma of acidities and reduction potentials of difluoromethylating agents. The strategy enabled achieving enantioselective difluoromethylation‐alkynylation reactions of olefins with difluoromethyl 4‐chlorophenyl sulfone.
Adsorption behavior of a solute is one of the most important factors to consider when designing a batch and a continuous liquid chromatographic separation process. In liquid chromatography, this ...behavior is based on the adsorption equilibrium between the liquid mobile-phase and solid stationary-phase. However, most retention models have been developed under a linear adsorption isotherm: very few researchers have investigated the relationship between the adsorption parameters and the mobile phase composition, and some empirical models have been introduced. In this work, adsorption isotherms were obtained by a frontal analysis for three small molecular compounds (benzene, toluene, and chlorobenzene) on a commercial C
18
bonded silica column. The absorption based on the Langmuir, Freundlich, and Langmuir-Freundlich models were investigated according to changes of the composition of methanol highly enriched eluent. The calculations and analysis of the coefficients obtained for the three models confirm that the adsorption data for solutes are best modeled with the Langmuir-Freundlich isotherm. In spite of the acceptable accuracy, Langmuir and Freundlich isotherm models couldn’t satisfactorily describe the mechanism and provide objective information on the physical nature of the absorption.
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