The reaction of malononitrile with Z nCl 2 and NaN 3 in the presence of 2,2’-bipyridine a nd water affords the first bis(tetrazole)Zn-complex intermediate,mono(2,2’-bipyridine)bis(tetrazolyl)methane aqua zinc*"...The reaction of malononitrile with Z nCl 2 and NaN 3 in the presence of 2,2’-bipyridine a nd water affords the first bis(tetrazole)Zn-complex intermediate,mono(2,2’-bipyridine)bis(tetrazolyl)methane aqua zinc*",[Zn(2,2’ -bpy)(BTZ)(H 2 O)]·(H 2 O) 2 (1)which gives a clue for Demko-Sharple ss’ tetrazole synthesis.Crystal data for1:C 13 H 18 N 10 O 4 Zn,M r =443.74,monoclinic,space group P2 1 /c,a=12.5705(18),b=16.078(2),c=9.1921(13)*!,β=95.010(3)°,V=1850.7(5)*! 3 ,Z =4.CCDC:197788.展开更多
The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.
Using four β-cyclodextrin derivatives, 2,6-di-O-benzyl-3-O-heptanonyl-β-CD, 2,6-di- O-benzyl-3-O-octanonyl-β-CD, 2,3-di-O-benzyl-6-O-heptanonyl-β-CD, and 2,3-di-O-benzyl -6-O- octanonyl-β-CD, as chiral stationary...Using four β-cyclodextrin derivatives, 2,6-di-O-benzyl-3-O-heptanonyl-β-CD, 2,6-di- O-benzyl-3-O-octanonyl-β-CD, 2,3-di-O-benzyl-6-O-heptanonyl-β-CD, and 2,3-di-O-benzyl -6-O- octanonyl-β-CD, as chiral stationary phases of capillary gas chromatography （CGC）, the enantiomers of Sharpless epoxides were well separated. The enantiomer excess values （e.e.%） of some chiral Sharpless epoxides were also determined successfully using these CDs.展开更多
The bond breaking and forming in chemical reactions is a typical rare event,which is one of the difficult problems in molecular dynamics simulations.Numerous enhanced sampling methods have been developed to extend the...The bond breaking and forming in chemical reactions is a typical rare event,which is one of the difficult problems in molecular dynamics simulations.Numerous enhanced sampling methods have been developed to extend the time scale covered by molecular simulations.However,the difficulties of obtaining appropriate collective variables from complicated reaction pathways and a controlled sampling over the desired phase space remain as challenges.Herein,we use MetaITS,which combines metadynamics and integrated tempered sampling,to increase the sampling efficiency for chemical reactions.Metadynamics with collective variables obtained by harmonic linear discriminant analysis can efficiently decrease the main energy barrier of chemical reaction.Meanwhile,integrated tempered sampling can enhance the exploration of other degrees of freedom.In this study,we applied the MetaITS method to two transition-metal-catalyzed organic reactions with complicated reaction coordinates.We simulated here a zirconocene-catalyzed propylene polymerization to investigate the regioselectivity and temperature effects.We also studied a Sharpless epoxidation reaction,for which both chiral products are observed through simulation.展开更多
Ⅰ. INTRODUCTIONChiral epoxy function group is often present in many native compounds with physiological activity. Asymmetric epoxidation is one of the important methods to prepare the chiral epoxy group.
Asymmetric epoxidation of methyl gibberellate by the modified Sharpless reagent at various temperature is described.Compound 8 and 9 can be used as the key intermediates for the syntheses of the polyhydroxygibberellins.
文摘The reaction of malononitrile with Z nCl 2 and NaN 3 in the presence of 2,2’-bipyridine a nd water affords the first bis(tetrazole)Zn-complex intermediate,mono(2,2’-bipyridine)bis(tetrazolyl)methane aqua zinc*",[Zn(2,2’ -bpy)(BTZ)(H 2 O)]·(H 2 O) 2 (1)which gives a clue for Demko-Sharple ss’ tetrazole synthesis.Crystal data for1:C 13 H 18 N 10 O 4 Zn,M r =443.74,monoclinic,space group P2 1 /c,a=12.5705(18),b=16.078(2),c=9.1921(13)*!,β=95.010(3)°,V=1850.7(5)*! 3 ,Z =4.CCDC:197788.
文摘The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.
基金This work was kindly supported by the National Natural Science Foundation of China(No.30471153,30170621and 21023478).
文摘Using four β-cyclodextrin derivatives, 2,6-di-O-benzyl-3-O-heptanonyl-β-CD, 2,6-di- O-benzyl-3-O-octanonyl-β-CD, 2,3-di-O-benzyl-6-O-heptanonyl-β-CD, and 2,3-di-O-benzyl -6-O- octanonyl-β-CD, as chiral stationary phases of capillary gas chromatography （CGC）, the enantiomers of Sharpless epoxides were well separated. The enantiomer excess values （e.e.%） of some chiral Sharpless epoxides were also determined successfully using these CDs.
基金supported by National Natural Science Foundation of China(grant nos.21927901,21821004,and 21873007 to Y.Q.G.,grant no.21933004 to Y.D.W.,grant nos.22273061 and 22003042 to Y.I.Y.)the Key-Area Research and Development Program of Guangdong Province(grant no.2020B0101350001 to Y.D.W.).
文摘The bond breaking and forming in chemical reactions is a typical rare event,which is one of the difficult problems in molecular dynamics simulations.Numerous enhanced sampling methods have been developed to extend the time scale covered by molecular simulations.However,the difficulties of obtaining appropriate collective variables from complicated reaction pathways and a controlled sampling over the desired phase space remain as challenges.Herein,we use MetaITS,which combines metadynamics and integrated tempered sampling,to increase the sampling efficiency for chemical reactions.Metadynamics with collective variables obtained by harmonic linear discriminant analysis can efficiently decrease the main energy barrier of chemical reaction.Meanwhile,integrated tempered sampling can enhance the exploration of other degrees of freedom.In this study,we applied the MetaITS method to two transition-metal-catalyzed organic reactions with complicated reaction coordinates.We simulated here a zirconocene-catalyzed propylene polymerization to investigate the regioselectivity and temperature effects.We also studied a Sharpless epoxidation reaction,for which both chiral products are observed through simulation.
基金Project supported by the National Natural Science Foundation of China
文摘Ⅰ. INTRODUCTIONChiral epoxy function group is often present in many native compounds with physiological activity. Asymmetric epoxidation is one of the important methods to prepare the chiral epoxy group.
文摘Asymmetric epoxidation of methyl gibberellate by the modified Sharpless reagent at various temperature is described.Compound 8 and 9 can be used as the key intermediates for the syntheses of the polyhydroxygibberellins.
