To investigate the recovery of amino alcohols as chiral auxiliaries, optically active p-benzyloxyphenylglycinol and its corresponding oxazolidine of 1-naphthylcarboxaldehyde were prepared. Grignard additions to the ox...To investigate the recovery of amino alcohols as chiral auxiliaries, optically active p-benzyloxyphenylglycinol and its corresponding oxazolidine of 1-naphthylcarboxaldehyde were prepared. Grignard additions to the oxazolidine followed by electrophilic quench and acidic hydrolysis afforded an aldehyde(compound 8)(later it was reduced to an alcohol, compound 9) in an excellent enantiomeric excess and a good recovery of the chiral amino alcohol. This research provides a model study of chiral amino alcohols in solid phase asymmetric synthesis.展开更多
The asymmetric alkylation reactions induced by non-cross-linked polystyrene supported cyclosulfamide chiral auxiliary occurred in moderate to good yields with a very high stereoselectivity(e.e.〉99%). Compared to no...The asymmetric alkylation reactions induced by non-cross-linked polystyrene supported cyclosulfamide chiral auxiliary occurred in moderate to good yields with a very high stereoselectivity(e.e.〉99%). Compared to non-supported cyclosulfamide chiral auxiliary, this chiral auxiliary can be recovered by simple precipitation and filtration, and could be reused at least four cycles without appreciable reduction in the yield or stereoselectivity.展开更多
A new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary was prepared and it was shown to be a particularly effective chiral auxiliary for asymmetric alkylations affording high yields and diastereoselectivitie...A new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary was prepared and it was shown to be a particularly effective chiral auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give a-alkylated carboxylic acids in good yield and in almost enatiomerically pure form.展开更多
The Mannich reaction of various 5-substituted and N-acyl substituted chiral hydantoins with a series of aldimines smoothly occurred with full stereochemical control. These Mannich adducts have been cleaved by alcoholy...The Mannich reaction of various 5-substituted and N-acyl substituted chiral hydantoins with a series of aldimines smoothly occurred with full stereochemical control. These Mannich adducts have been cleaved by alcoholysis to afford several synthetically useful chiral building blocks like β-amino esters and β-lactams in good yields and in enantiopure form.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
An intramolecular dehydrogenative homo-and hetero-coupling of phenols has been successfully developed for quick preparation of enantiopure axial diphenols under mild Cu(Ⅱ)-mediated conditions,using((4 S,5 S)-2,2-dime...An intramolecular dehydrogenative homo-and hetero-coupling of phenols has been successfully developed for quick preparation of enantiopure axial diphenols under mild Cu(Ⅱ)-mediated conditions,using((4 S,5 S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)dimethanol as the chiral auxiliary.The commercially available(R)-α-met hylbenzy la mine was identified as the best amine ligand for Cu(Ⅱ) in the reactions.A variety of homo/hetero bis-dihydroxylbenzoate substrates were examined,affording the corresponding axially chiral diphenols with satis factory to excellent diastereomeric ratios,and a representative scalable preparation was also attempted.A formal synthesis of natural product(+)-deoxyschizandrin has been achieved in this work using one axially chiral diphenol as the synthetic intermediate.展开更多
A highly efficient and practical synthesis for strained special scaffold of chiral endo-biarylnorbornane starting from available norbornadione was achieved with direct stereoselective dehydroxylation of tertiary alcoh...A highly efficient and practical synthesis for strained special scaffold of chiral endo-biarylnorbornane starting from available norbornadione was achieved with direct stereoselective dehydroxylation of tertiary alcohol as the key step,and the structure was illustrated by X-ray structural analysis.展开更多
The first example of the p-orbital overlap controlled enantioselectivity of Norrish type II photocyclization reaction was described. Irradiation of 5-methyl bicyclo[l. 1.1 ]pentanyl ketone with UV in the solid state a...The first example of the p-orbital overlap controlled enantioselectivity of Norrish type II photocyclization reaction was described. Irradiation of 5-methyl bicyclo[l. 1.1 ]pentanyl ketone with UV in the solid state as well as in the acetonitrile solution afforded the Norrish/Yang photocyclization compound as the sole product. Solid-state asymmetric photochemical studies using ionic chiral auxiliary technique led to the enantioselectivity as high as 60%. The results were rationalized by Xray single crystal structure.展开更多
Blastmycinone, a degradation product of the antibiotic antimycin A, was synthesized with a TiCl4-mediated asymmetric aldolization as the key step. Some unexpected yet interesting chemistry was also observed.
The diastereoselective three-component reaction of aldehydes, allyl bromide, and (S)-2-chlorotetrafluoroethancsulfinamide was achieved in the presence of zinc powder and titanium(IV) isopropoxide. Compared to (S...The diastereoselective three-component reaction of aldehydes, allyl bromide, and (S)-2-chlorotetrafluoroethancsulfinamide was achieved in the presence of zinc powder and titanium(IV) isopropoxide. Compared to (S)-tert-butanesulfinamide, the reaction used zinc powder instead of indium and better results were obtained with aromatic aldehydes. Moreover, opposite stereoselectivity is observed.展开更多
Asymmetric reduction of acetophenone O methyloxime with reagents in situ prepared from L proline and borane has been investigated. A series of conditions optimization were made, including an examination ...Asymmetric reduction of acetophenone O methyloxime with reagents in situ prepared from L proline and borane has been investigated. A series of conditions optimization were made, including an examination of the effect of the temperature of catalyst pretreatment, the temperature of reduction, the amount of borane, the additive, the solvent, the reducing agent and various chiral auxiliaries on the enantioselectivity. Under the optimal condition, ( S ) α phenylethylamine was obtained in 53% yield with 83 1% ee in the presence of 25 mol% L proline.展开更多
N-Acyl-β-hydroxy-4-phenyl-oxazolidinethiones could be rapidly converted into their ethyl thiol esters in high yields by treatment with EtSH at 0 ℃ in CH3CN or 9 : 1 (V : V) THF-H2O in the presence of a catalytic...N-Acyl-β-hydroxy-4-phenyl-oxazolidinethiones could be rapidly converted into their ethyl thiol esters in high yields by treatment with EtSH at 0 ℃ in CH3CN or 9 : 1 (V : V) THF-H2O in the presence of a catalytic amount of K2CO3.展开更多
The photochemical behavior of bicyclo[2.1.1]hexyl derivatives was investigated by irradiation with a 450 W medium-pressure mercury lamp in acetonitrile solution.The irradiation of methyl bicyclo[2.1.1]hexane-5-carbony...The photochemical behavior of bicyclo[2.1.1]hexyl derivatives was investigated by irradiation with a 450 W medium-pressure mercury lamp in acetonitrile solution.The irradiation of methyl bicyclo[2.1.1]hexane-5-carbonylbenzoate(1a)led to both Norrish type II cyclization and cleavage products with a molar ratio of 1∶2.2,whereas the irradiation of methyl 5-methylbicyclo[2.1.1]hexane-5-carbonylbenzoate(1b)afforded the only Norrish/Yang photocyclization compound as the sole product.Such results were illustrated by several geometric parameters for Norrish/Yang photoreaction asφ_(1),φ_(4) andβobtained from the crystal structures.Furthermore,asymmetric pho-tochemical studies using ionic chiral auxiliary technique were also conducted in the solid state.展开更多
All four isomers of a novel fl-branched unusual amino acid were designed and synthesized with high stereoselectivity (〉 90% de) and in 33%--44% overall yields by the use of 4(R/S)-5,5-dimethyl-4-phenyl-oxazolidin...All four isomers of a novel fl-branched unusual amino acid were designed and synthesized with high stereoselectivity (〉 90% de) and in 33%--44% overall yields by the use of 4(R/S)-5,5-dimethyl-4-phenyl-oxazolidin-2-one as the chiral auxiliary via asymmetric 1,4-Michael addition, direct or indirect azidation, hydrolysis and hydrogenation reactions.展开更多
This work reported a convenient method for the preparation of enantiomerically pure 6-aryl-2,2'-dihydroxy-1, l'- binaphthyl derivatives starting from the commercially available (R)-2,2'-hydroxy-l, l'-binaphthyl ...This work reported a convenient method for the preparation of enantiomerically pure 6-aryl-2,2'-dihydroxy-1, l'- binaphthyl derivatives starting from the commercially available (R)-2,2'-hydroxy-l, l'-binaphthyl [(R)-I] via bromi- nation, hydrolysis and Suzuki cross coupling reaction. This novel synthetie method was characterized with high re- gioselectivity, simple operation, mild reaction conditions, and excellent yield (up to 73%). On the other hand, we synthesized the target unknown compounds, which were confirmed by IR, 1H NMR, 13C NMR, MS and elementary analysis.展开更多
文摘To investigate the recovery of amino alcohols as chiral auxiliaries, optically active p-benzyloxyphenylglycinol and its corresponding oxazolidine of 1-naphthylcarboxaldehyde were prepared. Grignard additions to the oxazolidine followed by electrophilic quench and acidic hydrolysis afforded an aldehyde(compound 8)(later it was reduced to an alcohol, compound 9) in an excellent enantiomeric excess and a good recovery of the chiral amino alcohol. This research provides a model study of chiral amino alcohols in solid phase asymmetric synthesis.
基金Supported by the National Natural Science Foundation of China(No.21342002) and the College Students' Innovation and Entrepreneurship Training Plan of Hubei Province of China(No.201310512013).
文摘The asymmetric alkylation reactions induced by non-cross-linked polystyrene supported cyclosulfamide chiral auxiliary occurred in moderate to good yields with a very high stereoselectivity(e.e.〉99%). Compared to non-supported cyclosulfamide chiral auxiliary, this chiral auxiliary can be recovered by simple precipitation and filtration, and could be reused at least four cycles without appreciable reduction in the yield or stereoselectivity.
基金the National Natural Sciences Foundation of China(No.21342002)2011 National Major Scientific Instrument and Equipment Development Project(No.2011YQ12003505)for financial support
文摘A new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary was prepared and it was shown to be a particularly effective chiral auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give a-alkylated carboxylic acids in good yield and in almost enatiomerically pure form.
基金The authors would like to thank the financial supports from the National Natural Science Foundation of China(No.29902003,20132020 and 20175026),the Ministry of Science and Technology,the Chinese Ministry of Education and Tsinghua University.
基金Supported by the National Natural Science Foundation of China(No.21342002).
文摘The Mannich reaction of various 5-substituted and N-acyl substituted chiral hydantoins with a series of aldimines smoothly occurred with full stereochemical control. These Mannich adducts have been cleaved by alcoholysis to afford several synthetically useful chiral building blocks like β-amino esters and β-lactams in good yields and in enantiopure form.
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Financial support by National Key Research and Development Program of China(No.2018YFC0310900)the National Natural Science Foundation of China(Nos.21472087,21532002,21901112,21778031,21761142001)Jiangsu Provincial Department of Science and Technology(No.BK20190277)is greatly appreciated。
文摘An intramolecular dehydrogenative homo-and hetero-coupling of phenols has been successfully developed for quick preparation of enantiopure axial diphenols under mild Cu(Ⅱ)-mediated conditions,using((4 S,5 S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)dimethanol as the chiral auxiliary.The commercially available(R)-α-met hylbenzy la mine was identified as the best amine ligand for Cu(Ⅱ) in the reactions.A variety of homo/hetero bis-dihydroxylbenzoate substrates were examined,affording the corresponding axially chiral diphenols with satis factory to excellent diastereomeric ratios,and a representative scalable preparation was also attempted.A formal synthesis of natural product(+)-deoxyschizandrin has been achieved in this work using one axially chiral diphenol as the synthetic intermediate.
基金National Natural Science Foundation of China(Nos.30971934,31272074).
文摘A highly efficient and practical synthesis for strained special scaffold of chiral endo-biarylnorbornane starting from available norbornadione was achieved with direct stereoselective dehydroxylation of tertiary alcohol as the key step,and the structure was illustrated by X-ray structural analysis.
基金We are grateful to the financial supports from the National Natural Science Foundation of China (Nos. 20802013, 21002018, 21072038), the Natural Scientific Research Innovation Foundation in Harbin institute of Technology (Nos. 01107866, 01107986) and the Wenzhou Science and Technology Program (No. G20100056).
文摘The first example of the p-orbital overlap controlled enantioselectivity of Norrish type II photocyclization reaction was described. Irradiation of 5-methyl bicyclo[l. 1.1 ]pentanyl ketone with UV in the solid state as well as in the acetonitrile solution afforded the Norrish/Yang photocyclization compound as the sole product. Solid-state asymmetric photochemical studies using ionic chiral auxiliary technique led to the enantioselectivity as high as 60%. The results were rationalized by Xray single crystal structure.
基金Project supported by the National Natural Science Foundation of China (Nos. 20025207, 20272071, 20372075, 20321202), the Chinese Academy of Sciences (Knowledge Innovation Project, No. KGCX2-SW-209), and the Major State Basic Research Development Program (No. G2000077502).
文摘Blastmycinone, a degradation product of the antibiotic antimycin A, was synthesized with a TiCl4-mediated asymmetric aldolization as the key step. Some unexpected yet interesting chemistry was also observed.
基金Project supported by the National Natural Science Foundation of China (No. 20872166).
文摘The diastereoselective three-component reaction of aldehydes, allyl bromide, and (S)-2-chlorotetrafluoroethancsulfinamide was achieved in the presence of zinc powder and titanium(IV) isopropoxide. Compared to (S)-tert-butanesulfinamide, the reaction used zinc powder instead of indium and better results were obtained with aromatic aldehydes. Moreover, opposite stereoselectivity is observed.
文摘Asymmetric reduction of acetophenone O methyloxime with reagents in situ prepared from L proline and borane has been investigated. A series of conditions optimization were made, including an examination of the effect of the temperature of catalyst pretreatment, the temperature of reduction, the amount of borane, the additive, the solvent, the reducing agent and various chiral auxiliaries on the enantioselectivity. Under the optimal condition, ( S ) α phenylethylamine was obtained in 53% yield with 83 1% ee in the presence of 25 mol% L proline.
基金Project supported by the National Natural Science Foundation of China (Nos. 20025207, 20272071, 20372075 and 20321202), the Kn6wledge Innovation Project of the Chinese Academy of Sciences (No. KGCX2-SW-209), and the Major State Basic Research Development Program (No. G2000077502).
文摘N-Acyl-β-hydroxy-4-phenyl-oxazolidinethiones could be rapidly converted into their ethyl thiol esters in high yields by treatment with EtSH at 0 ℃ in CH3CN or 9 : 1 (V : V) THF-H2O in the presence of a catalytic amount of K2CO3.
基金We are grateful for the financial supports from the National Natural Science Foundation of China(Nos.21372055 and 21272047)the State Key Laboratory of Urban Water Resource and Environment(SKLUWRE)(No.2012DX10)+1 种基金the Fundamental Research Funds for the Central Universities(No.HIT.BRETIV.201310)the Zhejiang Natural Science Foundation(No.LY12B02009).
文摘The photochemical behavior of bicyclo[2.1.1]hexyl derivatives was investigated by irradiation with a 450 W medium-pressure mercury lamp in acetonitrile solution.The irradiation of methyl bicyclo[2.1.1]hexane-5-carbonylbenzoate(1a)led to both Norrish type II cyclization and cleavage products with a molar ratio of 1∶2.2,whereas the irradiation of methyl 5-methylbicyclo[2.1.1]hexane-5-carbonylbenzoate(1b)afforded the only Norrish/Yang photocyclization compound as the sole product.Such results were illustrated by several geometric parameters for Norrish/Yang photoreaction asφ_(1),φ_(4) andβobtained from the crystal structures.Furthermore,asymmetric pho-tochemical studies using ionic chiral auxiliary technique were also conducted in the solid state.
基金Project supported by the National Natural Science Foundation of China (Nos. 20472071, 20562014 and 30860342) and Natural Science Foundation of Yunnan Province (No. 2009cc017).
文摘All four isomers of a novel fl-branched unusual amino acid were designed and synthesized with high stereoselectivity (〉 90% de) and in 33%--44% overall yields by the use of 4(R/S)-5,5-dimethyl-4-phenyl-oxazolidin-2-one as the chiral auxiliary via asymmetric 1,4-Michael addition, direct or indirect azidation, hydrolysis and hydrogenation reactions.
文摘This work reported a convenient method for the preparation of enantiomerically pure 6-aryl-2,2'-dihydroxy-1, l'- binaphthyl derivatives starting from the commercially available (R)-2,2'-hydroxy-l, l'-binaphthyl [(R)-I] via bromi- nation, hydrolysis and Suzuki cross coupling reaction. This novel synthetie method was characterized with high re- gioselectivity, simple operation, mild reaction conditions, and excellent yield (up to 73%). On the other hand, we synthesized the target unknown compounds, which were confirmed by IR, 1H NMR, 13C NMR, MS and elementary analysis.