In view of the composition analysis and identification of ancient glass products, L1 regularization, K-Means cluster analysis, elbow rule and other methods were comprehensively used to build logical regression, cluste...In view of the composition analysis and identification of ancient glass products, L1 regularization, K-Means cluster analysis, elbow rule and other methods were comprehensively used to build logical regression, cluster analysis, hyper-parameter test and other models, and SPSS, Python and other tools were used to obtain the classification rules of glass products under different fluxes, sub classification under different chemical compositions, hyper-parameter K value test and rationality analysis. Research can provide theoretical support for the protection and restoration of ancient glass relics.展开更多
With the enhancement of environmental protection awareness, the requirements on drilling fluid are increasingly strict, and the use of ordinary oil-based drilling fluid has been strictly restricted. In order to solve ...With the enhancement of environmental protection awareness, the requirements on drilling fluid are increasingly strict, and the use of ordinary oil-based drilling fluid has been strictly restricted. In order to solve the environmental protection and oil-gas reservoir protection problems of offshore oil drilling, a new synthetic basic drilling fluid system is developed. The basic formula is as follows: a basic fluid (80% Linear a-olefin + 20% Simulated seawater) + 2.5% nano organobentonite + 3.5% emulsifier RHJ-5<sup>#</sup> + 2.5% fluid loss agent SDJ-1 + 1.5% CaO + the right amount of oil wetting barite to adjust the density, and a multifunctional oil and gas formation protective agent YRZ has been developed. The performance was evaluated using a high-low-high-temperature rheometer, a high-temperature and high-pressure demulsification voltage tester, and a high-temperature and high-pressure dynamic fluid loss meter. The results show that the developed synthetic based drilling fluid has good rheological property, demulsification voltage ≥ 500 V, temperature resistance up to 160°C, high temperature and high pressure filtration loss < 3.5 mL. After adding 2% - 5% YRZ into the basic formula of synthetic based drilling fluid, the permeability recovery value exceeds 90% and the reservoir protection effect is excellent. The new synthetic deepwater drilling fluid is expected to have a good application prospect in offshore deepwater drilling.展开更多
Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yield...Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yields, unsatisfactory stereo- and regioselectivity. Herein, we report a PET-triggered cascade reaction of silyl enolates that leads to the formation of angularly fused tricyclic scaffolds. The reaction exhibits broad substrate scope and excellent stereoselectivity. The regio- and stereoselectivity of this cascade reaction is elucidated via DFT calculation and conformational analysis.展开更多
Comprehensive Summary Alternative synthetic routes toward the tricyclic core of lindenane sesquiterpenoid are presented herein.The route A features an asymmetric organocatalysis enabling desymmetric silylation of diol...Comprehensive Summary Alternative synthetic routes toward the tricyclic core of lindenane sesquiterpenoid are presented herein.The route A features an asymmetric organocatalysis enabling desymmetric silylation of diol to establish the desired tertiary alcohol,while the route B consists of an acetate ring opening of chiral epoxy moiety.The common intermediate(16)in both routes can give rise to the core of lindenane sesquiterpenoid via an intramolecular cyclopropanation.展开更多
N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high...N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high nucleophilicity.Although NHOs have been emerging as a new type of organocatalyst and ligand for metal complexes in organic synthesis,chiral NHOmediated highly enantioselective organic transformations were still elusive.Herein,we developed a new type of chiral aminederived C_(2)-symmetric NHOs and employed them as efficient chiral bifunctional organocatalysts for asymmetricα-functionalization ofβ-ketoesters.With as low as 0.1 mol%catalyst loading,the desired amination and trifluoromethylthiolation products were afforded in good yields with high enantioselectivities(up to 99%yield and 99%ee).Experimental studies and theoretical calculation disclosed that hydrogen-bonding interaction upon protonation and other weak interaction between substrate and catalyst were crucial for the enantiocontrol.展开更多
Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles toβ-nitroenones orβ-nitroacrylates was established with chiral scandium catalysts.It enabled the construction o...Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles toβ-nitroenones orβ-nitroacrylates was established with chiral scandium catalysts.It enabled the construction of functionalized 3,3-disubstituted oxindoles,including terminal and internal vinyl groups in excellent yields and ee values.展开更多
An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric[3+2]cycloaddition of exocyclic enol ethers with p-quinones was achieved.The transformation was enabled by a chiral N,N′-dioxides/Tm^...An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric[3+2]cycloaddition of exocyclic enol ethers with p-quinones was achieved.The transformation was enabled by a chiral N,N′-dioxides/Tm^(Ⅲ)complex as the Lewis acid catalyst and afforded a series of enantiomerically enriched benzannulated spiroketal derivatives in good yields(up to 99%)and enantioselectivities(up to 98%ee).Topographic steric maps and distribution of the buried volumes of the catalysts via Cavallo’s SambVca 2 tool were used to elucidate the enantioinduction raised by the ligands and the metal ions.展开更多
Chiral Lewis acid-catalyzed enantioselective nitrooxylation of cyclic and acyclicβ-keto amides/esters with hypervalent iodine(III)reagents is reported.A number ofα-nitrooxy-β-keto amides/esters were obtained with g...Chiral Lewis acid-catalyzed enantioselective nitrooxylation of cyclic and acyclicβ-keto amides/esters with hypervalent iodine(III)reagents is reported.A number ofα-nitrooxy-β-keto amides/esters were obtained with good yields and high enantioselectivities by using bench-stable nitratobenziodoxole under mild conditions.展开更多
A highly efficient dearomatization of 3-(2-isocyanoethyl)indoles with in situ generated nitrile imines has been developed through a nucleophilic/Friedel–Crafts/aza-Mannich type cascade and 1,3-dipolar cyclo-addition ...A highly efficient dearomatization of 3-(2-isocyanoethyl)indoles with in situ generated nitrile imines has been developed through a nucleophilic/Friedel–Crafts/aza-Mannich type cascade and 1,3-dipolar cyclo-addition reaction under catalyst-free and mild reaction conditions.This strategy offers a novel and con-venient route to the rapid assembly of a wide range of unprecedented polycyclic indoline scaffolds in moderate to excellent yields and diastereoselectivities.展开更多
Asymmetric nucleophilic addition of 3-substituted NBoc oxindoles to 3-bromooxindoles was designed to directly construct hetero-3,3′-bisoxindoles,with varying vicinal quaternary carbon stereocenters and N-substituents...Asymmetric nucleophilic addition of 3-substituted NBoc oxindoles to 3-bromooxindoles was designed to directly construct hetero-3,3′-bisoxindoles,with varying vicinal quaternary carbon stereocenters and N-substituents.The reaction progressed efficiently with high yields,good diastereo-and enantioselectivity(up to>99%ee)under mild reaction conditions catalyzed by chiral N,N′-dioxide/metal complexes.This methodology enabled the facile transformation of the generated hetero-3,3’-bisoxindoles into diverse hexahydropyrroloindole alkaloids with potential antiparasitic and anticancer properties.展开更多
文摘In view of the composition analysis and identification of ancient glass products, L1 regularization, K-Means cluster analysis, elbow rule and other methods were comprehensively used to build logical regression, cluster analysis, hyper-parameter test and other models, and SPSS, Python and other tools were used to obtain the classification rules of glass products under different fluxes, sub classification under different chemical compositions, hyper-parameter K value test and rationality analysis. Research can provide theoretical support for the protection and restoration of ancient glass relics.
文摘With the enhancement of environmental protection awareness, the requirements on drilling fluid are increasingly strict, and the use of ordinary oil-based drilling fluid has been strictly restricted. In order to solve the environmental protection and oil-gas reservoir protection problems of offshore oil drilling, a new synthetic basic drilling fluid system is developed. The basic formula is as follows: a basic fluid (80% Linear a-olefin + 20% Simulated seawater) + 2.5% nano organobentonite + 3.5% emulsifier RHJ-5<sup>#</sup> + 2.5% fluid loss agent SDJ-1 + 1.5% CaO + the right amount of oil wetting barite to adjust the density, and a multifunctional oil and gas formation protective agent YRZ has been developed. The performance was evaluated using a high-low-high-temperature rheometer, a high-temperature and high-pressure demulsification voltage tester, and a high-temperature and high-pressure dynamic fluid loss meter. The results show that the developed synthetic based drilling fluid has good rheological property, demulsification voltage ≥ 500 V, temperature resistance up to 160°C, high temperature and high pressure filtration loss < 3.5 mL. After adding 2% - 5% YRZ into the basic formula of synthetic based drilling fluid, the permeability recovery value exceeds 90% and the reservoir protection effect is excellent. The new synthetic deepwater drilling fluid is expected to have a good application prospect in offshore deepwater drilling.
基金supported by NSFC(21925106,U19A2014)Si-chuan University(2020SCUNL204)Department of Science and Technology of Sichuan Province(2023NSFSC0105).
文摘Photo-induced electron transfer (PET) of silyl enol ethers has been employed to synthesize several fused ring systems. However, the method has limited applicability due to its narrow substrate scope, low product yields, unsatisfactory stereo- and regioselectivity. Herein, we report a PET-triggered cascade reaction of silyl enolates that leads to the formation of angularly fused tricyclic scaffolds. The reaction exhibits broad substrate scope and excellent stereoselectivity. The regio- and stereoselectivity of this cascade reaction is elucidated via DFT calculation and conformational analysis.
文摘Comprehensive Summary Alternative synthetic routes toward the tricyclic core of lindenane sesquiterpenoid are presented herein.The route A features an asymmetric organocatalysis enabling desymmetric silylation of diol to establish the desired tertiary alcohol,while the route B consists of an acetate ring opening of chiral epoxy moiety.The common intermediate(16)in both routes can give rise to the core of lindenane sesquiterpenoid via an intramolecular cyclopropanation.
基金supported by the National Natural Science Foundation of China(92056107,22271199,21801175)the Sichuan University(2020SCUNL204)。
文摘N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high nucleophilicity.Although NHOs have been emerging as a new type of organocatalyst and ligand for metal complexes in organic synthesis,chiral NHOmediated highly enantioselective organic transformations were still elusive.Herein,we developed a new type of chiral aminederived C_(2)-symmetric NHOs and employed them as efficient chiral bifunctional organocatalysts for asymmetricα-functionalization ofβ-ketoesters.With as low as 0.1 mol%catalyst loading,the desired amination and trifluoromethylthiolation products were afforded in good yields with high enantioselectivities(up to 99%yield and 99%ee).Experimental studies and theoretical calculation disclosed that hydrogen-bonding interaction upon protonation and other weak interaction between substrate and catalyst were crucial for the enantiocontrol.
基金financial support from the National Natural Science Foundation of China(No.21890723)。
文摘Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles toβ-nitroenones orβ-nitroacrylates was established with chiral scandium catalysts.It enabled the construction of functionalized 3,3-disubstituted oxindoles,including terminal and internal vinyl groups in excellent yields and ee values.
基金the National Natural Science Foundation of China(Nos.21890723 and 21921002)the Science and Technology Department of Sichuan Province(Nos.2021YJ0561)for financial support.
文摘An efficient synthesis of chiral benzannulated spiroketals via catalytic asymmetric[3+2]cycloaddition of exocyclic enol ethers with p-quinones was achieved.The transformation was enabled by a chiral N,N′-dioxides/Tm^(Ⅲ)complex as the Lewis acid catalyst and afforded a series of enantiomerically enriched benzannulated spiroketal derivatives in good yields(up to 99%)and enantioselectivities(up to 98%ee).Topographic steric maps and distribution of the buried volumes of the catalysts via Cavallo’s SambVca 2 tool were used to elucidate the enantioinduction raised by the ligands and the metal ions.
基金We appreciate the National Natural Science Foundation of China(22071160)for financial support.
文摘Chiral Lewis acid-catalyzed enantioselective nitrooxylation of cyclic and acyclicβ-keto amides/esters with hypervalent iodine(III)reagents is reported.A number ofα-nitrooxy-β-keto amides/esters were obtained with good yields and high enantioselectivities by using bench-stable nitratobenziodoxole under mild conditions.
基金The financial support was provided by the National Natural Science Foundation of China(no.22001181 and 22077090)the Sichuan Science and Technology Program(2021YJ0407).
文摘A highly efficient dearomatization of 3-(2-isocyanoethyl)indoles with in situ generated nitrile imines has been developed through a nucleophilic/Friedel–Crafts/aza-Mannich type cascade and 1,3-dipolar cyclo-addition reaction under catalyst-free and mild reaction conditions.This strategy offers a novel and con-venient route to the rapid assembly of a wide range of unprecedented polycyclic indoline scaffolds in moderate to excellent yields and diastereoselectivities.
基金support from the National Natural Science Foundation of China(grant nos.21625205 and U19A2014).
文摘Asymmetric nucleophilic addition of 3-substituted NBoc oxindoles to 3-bromooxindoles was designed to directly construct hetero-3,3′-bisoxindoles,with varying vicinal quaternary carbon stereocenters and N-substituents.The reaction progressed efficiently with high yields,good diastereo-and enantioselectivity(up to>99%ee)under mild reaction conditions catalyzed by chiral N,N′-dioxide/metal complexes.This methodology enabled the facile transformation of the generated hetero-3,3’-bisoxindoles into diverse hexahydropyrroloindole alkaloids with potential antiparasitic and anticancer properties.
