A novel and efficient method for distinguishing between chiral diols and diphenols has been established through the use of^(19)F NMR spectroscopy.Central to this system's efficacy is a chiral amine,strategically m...A novel and efficient method for distinguishing between chiral diols and diphenols has been established through the use of^(19)F NMR spectroscopy.Central to this system's efficacy is a chiral amine,strategically modified with a CF_(3)group.This amine reacts in-situ with 2-formylphenylboronic acid to create a chiral^(19)F-labeled probe.This probe demonstrates discriminatory capabilities by interacting with hydroxy-containing analytes to form boronic esters.These esters produce distinct^(19)F NMR signals that vary according to their stereoconfiguration,facilitating accurate chiral differentiation.The method's resolution capacity was demonstrated by successfully identifying 12 distinct chiral analytes(six pairs of enantiomers)in complex mixtures,highlighting its extensive potential in diverse chiral analysis applications.展开更多
Beryllium fluorides are widely used in protein phosphorylation studies to get stable transition state analogs or near attack conformers,which has attracted much attention.BeF_(3)^(−) is one of the optimal phosphoryl(P...Beryllium fluorides are widely used in protein phosphorylation studies to get stable transition state analogs or near attack conformers,which has attracted much attention.BeF_(3)^(−) is one of the optimal phosphoryl(PO_(3)^(−))analogs for its identical geometry and charge,and Mg^(2+) naturally participates in the phosphoryl binding in biological systems.In solutions,BeF_(3)^(−) coexists with other beryllium fluorides(BeF_(4)^(2−),BeF_(2) and BeF^(+))and magnesium fluorides,and there are equilibriums between these species.In this article,^(19)F NMR spectroscopy was applied to the investigation of the impact of magnesium(Ⅱ)on beryllium fluorides.It has been found that when Mg^(2+) was introduced into the solutions,the chemical shifts,the intensities and the line widths of ^(19)F signals of various beryllium fluoride complexes were changed.After ionic strength correction,these effects were remarkable only for 2 BeF_(4)^(2−) and BeF_(3)^(−),especially BeF_(4)^(2−),when the concentration of the fluoride ion is relatively low.Mechanism of the effects is proposed which involves ion pair formation between Mg^(2+) and beryllium fluorides.展开更多
The basic approximation of the MNDO method is applied to the SCF-MO theory of nu- clear magnetic shielding constants.Gauge-invariant atomic orbitais(GIAO)and derived equations are used to cal- culate NMR chemical shif...The basic approximation of the MNDO method is applied to the SCF-MO theory of nu- clear magnetic shielding constants.Gauge-invariant atomic orbitais(GIAO)and derived equations are used to cal- culate NMR chemical shifts.A more simple and effective calculation of integration for operators 1/r_M,L_M and L_M/r_M described in our previous paper is used.By proper selection of MNDO parameters together with the two-center approximation,a satisfactory agreement between computational and experimental ^(13)C and ^(19)F chemi- cal shifts is obtained for a representative set of fluorides.展开更多
Synthesis and anionic polymerization of the fluorine-substituted phenyl methacrylates are herein reported. A series of monodi-, and multi-substituted fluorophenyl methacrylates H2C=C（CH3）C（O）OC6H4F-4 （M^1a）, H2...Synthesis and anionic polymerization of the fluorine-substituted phenyl methacrylates are herein reported. A series of monodi-, and multi-substituted fluorophenyl methacrylates H2C=C（CH3）C（O）OC6H4F-4 （M^1a）, H2C=C（CH3）C（O）OC6H4F-3 （M^1b）, HEC=C（CH3）C（O）OC6H3F2-2,4 （M^2）, H2C=C（CH3）C（O）OC6H2F3-2,3,4 （M^3）, H2C=C（CH3）C（O）OC6HF4-2,3,5,6 （M^4）, and H2C=C（CH3）C（O）OC6F5 （M^5） were synthesized and characterized. Initially, the polymerization was carded out on the monomer M^1a by using nBuLi, tBuLi, and KH as the respective catalysts; this approach produced the polymers in yields of 12%-50%, but with lower molecular weights. Similar results were obtained by using tBuLi for catalytically polymerizing the other five monomers. By introducing a co-catalyst MeAl（BHT）2, the catalysts Nail, LiH, and tBuOLi each were tested to polymerize M^1a, which gave the polymers in very low yields （3%-7%）. Polymer yields of 13%-27% were obtained by each of the catalysts LiAlH4, nBuLi, PhLi, and tBuLi in connection with MeAI（BHT）2, but a better yield （61%） was achieved with KH/MeAl（BHT）2. The KH/MeAl（BHT）2 catalyst system was further employed to polymerize M^1b and M^2, which afforded respective polymer yields of 12%-63% and 10%-53%, depending on the molar ratios of KH：MeAl（BHT）2 as well as on the monomer concentrations. All of the polymers produced were syndiotactically rich in structure, as indicated by either ^1H or ^19F NMR data. The polymerization mechanism by the combined catalyst system is proposed.展开更多
基金supported by the National Key Research and Development Program(2021YFF0701700)the National Natural Science Foundation of China(22271305).
文摘A novel and efficient method for distinguishing between chiral diols and diphenols has been established through the use of^(19)F NMR spectroscopy.Central to this system's efficacy is a chiral amine,strategically modified with a CF_(3)group.This amine reacts in-situ with 2-formylphenylboronic acid to create a chiral^(19)F-labeled probe.This probe demonstrates discriminatory capabilities by interacting with hydroxy-containing analytes to form boronic esters.These esters produce distinct^(19)F NMR signals that vary according to their stereoconfiguration,facilitating accurate chiral differentiation.The method's resolution capacity was demonstrated by successfully identifying 12 distinct chiral analytes(six pairs of enantiomers)in complex mixtures,highlighting its extensive potential in diverse chiral analysis applications.
基金This work was supported by grants from the National Basic Research Program of China(No.2013CB910200)the Natural Science Foundation of China(No.21173257).
文摘Beryllium fluorides are widely used in protein phosphorylation studies to get stable transition state analogs or near attack conformers,which has attracted much attention.BeF_(3)^(−) is one of the optimal phosphoryl(PO_(3)^(−))analogs for its identical geometry and charge,and Mg^(2+) naturally participates in the phosphoryl binding in biological systems.In solutions,BeF_(3)^(−) coexists with other beryllium fluorides(BeF_(4)^(2−),BeF_(2) and BeF^(+))and magnesium fluorides,and there are equilibriums between these species.In this article,^(19)F NMR spectroscopy was applied to the investigation of the impact of magnesium(Ⅱ)on beryllium fluorides.It has been found that when Mg^(2+) was introduced into the solutions,the chemical shifts,the intensities and the line widths of ^(19)F signals of various beryllium fluoride complexes were changed.After ionic strength correction,these effects were remarkable only for 2 BeF_(4)^(2−) and BeF_(3)^(−),especially BeF_(4)^(2−),when the concentration of the fluoride ion is relatively low.Mechanism of the effects is proposed which involves ion pair formation between Mg^(2+) and beryllium fluorides.
文摘The basic approximation of the MNDO method is applied to the SCF-MO theory of nu- clear magnetic shielding constants.Gauge-invariant atomic orbitais(GIAO)and derived equations are used to cal- culate NMR chemical shifts.A more simple and effective calculation of integration for operators 1/r_M,L_M and L_M/r_M described in our previous paper is used.By proper selection of MNDO parameters together with the two-center approximation,a satisfactory agreement between computational and experimental ^(13)C and ^(19)F chemi- cal shifts is obtained for a representative set of fluorides.
基金supported by the National Basic Research Program of China(2012CB821704)the National Natural Science Foundation of China(20972129)the Innovative Research Team Program(IRT1036,J1310024)
文摘Synthesis and anionic polymerization of the fluorine-substituted phenyl methacrylates are herein reported. A series of monodi-, and multi-substituted fluorophenyl methacrylates H2C=C（CH3）C（O）OC6H4F-4 （M^1a）, H2C=C（CH3）C（O）OC6H4F-3 （M^1b）, HEC=C（CH3）C（O）OC6H3F2-2,4 （M^2）, H2C=C（CH3）C（O）OC6H2F3-2,3,4 （M^3）, H2C=C（CH3）C（O）OC6HF4-2,3,5,6 （M^4）, and H2C=C（CH3）C（O）OC6F5 （M^5） were synthesized and characterized. Initially, the polymerization was carded out on the monomer M^1a by using nBuLi, tBuLi, and KH as the respective catalysts; this approach produced the polymers in yields of 12%-50%, but with lower molecular weights. Similar results were obtained by using tBuLi for catalytically polymerizing the other five monomers. By introducing a co-catalyst MeAl（BHT）2, the catalysts Nail, LiH, and tBuOLi each were tested to polymerize M^1a, which gave the polymers in very low yields （3%-7%）. Polymer yields of 13%-27% were obtained by each of the catalysts LiAlH4, nBuLi, PhLi, and tBuLi in connection with MeAI（BHT）2, but a better yield （61%） was achieved with KH/MeAl（BHT）2. The KH/MeAl（BHT）2 catalyst system was further employed to polymerize M^1b and M^2, which afforded respective polymer yields of 12%-63% and 10%-53%, depending on the molar ratios of KH：MeAl（BHT）2 as well as on the monomer concentrations. All of the polymers produced were syndiotactically rich in structure, as indicated by either ^1H or ^19F NMR data. The polymerization mechanism by the combined catalyst system is proposed.
