Three novel chiral binuclear Mn(Ⅲ)-Schiff-base complexes have been synthesized and the application of these complexes in the asymmetric epoxidation of trans-stilbene is described, catalytic mechanism is also discusse...Three novel chiral binuclear Mn(Ⅲ)-Schiff-base complexes have been synthesized and the application of these complexes in the asymmetric epoxidation of trans-stilbene is described, catalytic mechanism is also discussed briefly.展开更多
A series of chiral salen-Mn（Ⅲ） complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-...A series of chiral salen-Mn（Ⅲ） complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-dimethylpyridine N-oxide as proximal ligands, respectively. Moderate to high enantioselectivity and acceptable yields were achieved when NaClO was used as terminal oxidant under CH2Cl2/H2O biphasic media. Methyl iodide was found to be an effective additive to accelerate the epoxidation, possibly owing to the formation of quaternary ammonium units on catalysts, which may facilitate the reaction in an oil/water biphasic medium. The subsequent stimulation experiment was carried out, and the resulting ESI-HRMS analysis revealed the formation of a novel （salen）manganese（m） intermediate featuring two quaternary ammonium units, and bearing a pyridine N-oxide and a molecule of water simultaneously axially-coordinated backbone.展开更多
Chiral phase-transfer catalysts, derived from cinchona alkaloids and Fréchet dendritic wedges up to generation two, have been synthesized. These chiral dendritic molecules have been used as PTCs in the epoxidatio...Chiral phase-transfer catalysts, derived from cinchona alkaloids and Fréchet dendritic wedges up to generation two, have been synthesized. These chiral dendritic molecules have been used as PTCs in the epoxidation of α, β-enones, showing a moderate level of asymmetric induction.展开更多
We report herein a formal asymmetric epoxidation of arylalkanes enabled by a one-pot dual-catalysts system comprising a pincer Ir catalyst for alkane dehydrogenation-alkene isomerization(AD-ISO)and a chiral ketone cat...We report herein a formal asymmetric epoxidation of arylalkanes enabled by a one-pot dual-catalysts system comprising a pincer Ir catalyst for alkane dehydrogenation-alkene isomerization(AD-ISO)and a chiral ketone catalyst for asymmetric alkene epoxidation.This protocol provides a catalytic method for the synthesis of aryl epoxides in useful yields with high regio-and stereoselectivity directly from readily available alkyl arenes.Stereospecific derivatizations of the epoxidation product allow access to various enantioenriched compounds.展开更多
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.
Jacobsen's catalyst was immobilized onto SBA-15 by multi-step grafting, and this heterogenized catalyst exhibited comparable catalytic performance with the corresponding homogeneous counterpart for the epoxidation...Jacobsen's catalyst was immobilized onto SBA-15 by multi-step grafting, and this heterogenized catalyst exhibited comparable catalytic performance with the corresponding homogeneous counterpart for the epoxidation of alkenes, and the catalyst could be recycled effectively several times.展开更多
A chiral synthesis of the C11-16+C27 segment of epomilone A is described using inexpensive L-(-)-malic acid as staring materinal and using Sharpless asymmetric epoxidahon for introduction of the desired 12, 13 epoxide.
The stereoselective synthesis of (-)-slaframine has been achieved by utilizing the Sharpless asymmetric epoxidation of divinylcarbinol (2) and the regio-selective dihydroxylation of compound 4 as the key steps.
Starting from propargyl alcohol （12）, and on the basis of Zhou＇s modified Sharpless asymmetric epoxidation, the sex pheromone of the Gypsy moth, disparlure （＋）-8 and its enantiomer （-）-8 have been synthesized,...Starting from propargyl alcohol （12）, and on the basis of Zhou＇s modified Sharpless asymmetric epoxidation, the sex pheromone of the Gypsy moth, disparlure （＋）-8 and its enantiomer （-）-8 have been synthesized, each in six steps, with overall yields of 29% for （＋）-8 and 27% for （-）-8 （ee〉98%）. The use of the sequential coupling tactic renders the method flexible, which is applicable to the synthesis of other cis-epoxy pheromones.展开更多
Asymmetric epoxidation of N-enoylsultams （1, 3-15） incorporating a variety of chiral sultams as the chiral induction elements with UHP/TFAA has been studied. Both diastereomeric isomers of epoxides （2, 16-28） were...Asymmetric epoxidation of N-enoylsultams （1, 3-15） incorporating a variety of chiral sultams as the chiral induction elements with UHP/TFAA has been studied. Both diastereomeric isomers of epoxides （2, 16-28） were obtained in high yield and moderate to high optical purity.展开更多
Three new homochiral bis-diamine-bridged bi-Mn（salen） complexes were synthesized. Their catalysis on asymmetric epoxidation of a-methylstyrene, styrene and indene was studied with NaC10 and m-CPBA as oxidants respec...Three new homochiral bis-diamine-bridged bi-Mn（salen） complexes were synthesized. Their catalysis on asymmetric epoxidation of a-methylstyrene, styrene and indene was studied with NaC10 and m-CPBA as oxidants respectively. This homogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to the Jacobsen＇s catalyst in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the catalyst could be conveniently recovered and reused at least five times without significant losses of both activity and enantioselectivity. Specially, it also could be efficiently used in large-scale reactions with superior catalytic disposition being maintained at the same level, which provided the potential for the applications in industry. The effect of axial bases, temperature and solvent on activity and enantioselectivity of the catalytic system were also studied.展开更多
Studies on the synthesis of antifungal and anticancer natural product,pseudolaric acid B,have led to the enantioselective synthesis of di-epi-trans-fused[5-7]-bicyclic co re skeleton.The synthesis was achieved in 10 l...Studies on the synthesis of antifungal and anticancer natural product,pseudolaric acid B,have led to the enantioselective synthesis of di-epi-trans-fused[5-7]-bicyclic co re skeleton.The synthesis was achieved in 10 linear steps,which features the Sharpless asymmetric epoxidation,cyanide-opening reaction of epoxide,and intramolecular[5+2]cycloaddition reaction as the key transformations.The stereochemistry was determined by the X-ray crystallographic analysis.展开更多
The antibiotic （-）-anisomycin was synthesized starting from D-tyrosine using Sharpless asymmetric epoxidation as a key reaction followed by formation and hydrolysis of oxazoline set up all chiral center.
(+)-Preussin (1) and its 5-epimer were synthesized from the divinylcarbinol (3) with Sharpless asymmetric epoxidation of 3 and the oxidative cyclization of 9 with PDC as the key steps.
文摘Three novel chiral binuclear Mn(Ⅲ)-Schiff-base complexes have been synthesized and the application of these complexes in the asymmetric epoxidation of trans-stilbene is described, catalytic mechanism is also discussed briefly.
基金Project supported by the National Natural Science Founclation of China （No. 20571035）, the Gansu Natural Science Foundation of China （No. 3ZS051-A25-003）.Acknowledgement The authors are grateful to the Instrumental Analysis and Research Center of Lanzhou University and State Key Laboratory of Applied 0rganic Chemistry for providing instrumentation facilities.
文摘A series of chiral salen-Mn（Ⅲ） complexes featuring two tertiary amine units were synthesized and employed in the enantioselective epoxidation of unfunctionalized alkenes in the presence of pyridine N-oxide and 2,6-dimethylpyridine N-oxide as proximal ligands, respectively. Moderate to high enantioselectivity and acceptable yields were achieved when NaClO was used as terminal oxidant under CH2Cl2/H2O biphasic media. Methyl iodide was found to be an effective additive to accelerate the epoxidation, possibly owing to the formation of quaternary ammonium units on catalysts, which may facilitate the reaction in an oil/water biphasic medium. The subsequent stimulation experiment was carried out, and the resulting ESI-HRMS analysis revealed the formation of a novel （salen）manganese（m） intermediate featuring two quaternary ammonium units, and bearing a pyridine N-oxide and a molecule of water simultaneously axially-coordinated backbone.
文摘Chiral phase-transfer catalysts, derived from cinchona alkaloids and Fréchet dendritic wedges up to generation two, have been synthesized. These chiral dendritic molecules have been used as PTCs in the epoxidation of α, β-enones, showing a moderate level of asymmetric induction.
基金Financial supportfrom the National Key R&D Program of China(Nos.2021YFA1500100,2021YFA1501700)the National Natural Science Foundation of China(Nos.21825109,21821002,21732006,22072178)+1 种基金CAS Youth Interdisciplinary Team(No.JCTD-2021-11)the K.C.Wong Education Foundation,and Ningbo Municipal Bureau of Science and Technology(No.2019B10096)is gratefully acknowledged.
文摘We report herein a formal asymmetric epoxidation of arylalkanes enabled by a one-pot dual-catalysts system comprising a pincer Ir catalyst for alkane dehydrogenation-alkene isomerization(AD-ISO)and a chiral ketone catalyst for asymmetric alkene epoxidation.This protocol provides a catalytic method for the synthesis of aryl epoxides in useful yields with high regio-and stereoselectivity directly from readily available alkyl arenes.Stereospecific derivatizations of the epoxidation product allow access to various enantioenriched compounds.
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.
文摘Jacobsen's catalyst was immobilized onto SBA-15 by multi-step grafting, and this heterogenized catalyst exhibited comparable catalytic performance with the corresponding homogeneous counterpart for the epoxidation of alkenes, and the catalyst could be recycled effectively several times.
文摘A chiral synthesis of the C11-16+C27 segment of epomilone A is described using inexpensive L-(-)-malic acid as staring materinal and using Sharpless asymmetric epoxidahon for introduction of the desired 12, 13 epoxide.
文摘The stereoselective synthesis of (-)-slaframine has been achieved by utilizing the Sharpless asymmetric epoxidation of divinylcarbinol (2) and the regio-selective dihydroxylation of compound 4 as the key steps.
基金This work was search Program supported by the （973 Program） National Basic Reof China （No. 2010CB833200）, the National Natural Science Foundation of China （No. 20832005） and the Natural Science Foundation of Fujian Province of China （No. 2011J01054）.
文摘Starting from propargyl alcohol （12）, and on the basis of Zhou＇s modified Sharpless asymmetric epoxidation, the sex pheromone of the Gypsy moth, disparlure （＋）-8 and its enantiomer （-）-8 have been synthesized, each in six steps, with overall yields of 29% for （＋）-8 and 27% for （-）-8 （ee〉98%）. The use of the sequential coupling tactic renders the method flexible, which is applicable to the synthesis of other cis-epoxy pheromones.
文摘Asymmetric epoxidation of N-enoylsultams （1, 3-15） incorporating a variety of chiral sultams as the chiral induction elements with UHP/TFAA has been studied. Both diastereomeric isomers of epoxides （2, 16-28） were obtained in high yield and moderate to high optical purity.
基金financially supported by National Ministry of Science and Technology Innovation Fund for High-tech Small and Medium Enterprise Technology (09C26215112399)National Ministry of Human Resources and Social Security Start-up Support Projects for Students Returned to Business, Office of Human Resources and Social Security Issued 2009 (143)
文摘Three new homochiral bis-diamine-bridged bi-Mn（salen） complexes were synthesized. Their catalysis on asymmetric epoxidation of a-methylstyrene, styrene and indene was studied with NaC10 and m-CPBA as oxidants respectively. This homogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to the Jacobsen＇s catalyst in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the catalyst could be conveniently recovered and reused at least five times without significant losses of both activity and enantioselectivity. Specially, it also could be efficiently used in large-scale reactions with superior catalytic disposition being maintained at the same level, which provided the potential for the applications in industry. The effect of axial bases, temperature and solvent on activity and enantioselectivity of the catalytic system were also studied.
基金the financial support from the National Natural Science Foundation of China(Nos.21302078,21572089,21732001,21672017)the Program for Changjiang Scholars and the Innovative Research Team in Universities(PCSIRT:No.IRT_15R28)+3 种基金the State Key Basic Research Program of the PRC(No.2018YFC0310900)Shenzhen Science and Technology Innovation Committee(No.JCYJ20180504165454447)Shenzhen Basic Research Program(No.20180202)the National Ten Thousand Talent Program(the Leading Talent Tier)。
文摘Studies on the synthesis of antifungal and anticancer natural product,pseudolaric acid B,have led to the enantioselective synthesis of di-epi-trans-fused[5-7]-bicyclic co re skeleton.The synthesis was achieved in 10 linear steps,which features the Sharpless asymmetric epoxidation,cyanide-opening reaction of epoxide,and intramolecular[5+2]cycloaddition reaction as the key transformations.The stereochemistry was determined by the X-ray crystallographic analysis.
基金support from The First Hospital of Jilin University
文摘The antibiotic （-）-anisomycin was synthesized starting from D-tyrosine using Sharpless asymmetric epoxidation as a key reaction followed by formation and hydrolysis of oxazoline set up all chiral center.
基金Project supported by the National Natural Science Foundation of China
文摘(+)-Preussin (1) and its 5-epimer were synthesized from the divinylcarbinol (3) with Sharpless asymmetric epoxidation of 3 and the oxidative cyclization of 9 with PDC as the key steps.
