So far,there have been 4 methods to control chirality including the use of chiral auxiliaries,reagents,solvents,and catalysts documented in literature and textbooks.Among them,asymmetric catalysts are normally divided...So far,there have been 4 methods to control chirality including the use of chiral auxiliaries,reagents,solvents,and catalysts documented in literature and textbooks.Among them,asymmetric catalysts are normally divided into homogeneous and heterogeneous catalysis.In this report,we present a new type of asymmetric control—asymmetric catalysis via chiral aggregates that would not belong to the above categories.This new strategy is represented by catalytic asymmetric dihydroxylation reaction of olefins in which chiral ligands are aggregated by taking advantage of typical aggregation-induced emission systems containing tetrahydrofuran and H_(2)O cosolvents.It was proven that the chiral induction can be enhanced from er of 78:22 to 97:3 simply by changing the ratios of these 2 cosolvents.展开更多
Orientational chirality was discovered and characterized by a C(sp)-C(sp3)axis-anchored chiral center and a remotely anchored blocker.X-ray structural analysis proved that orientatiomers are stabilized by through-spac...Orientational chirality was discovered and characterized by a C(sp)-C(sp3)axis-anchored chiral center and a remotely anchored blocker.X-ray structural analysis proved that orientatiomers are stabilized by through-space functional groups,making it possible for 1 R-or S-chiral center to exhibit 3 orientational isomers simply by rotating operations.A new model system was proposed,fundamentally different from the traditional Felkin-Ahn-type or Cram-type models.In these traditional models,chiral C(sp^(3))center and blocking C(sp^(3))carbons are connected adjacently,and there exist 6 energy barriers during rotating along the C(sp^(2))-C(sp^(3))axis.In comparison,the present orientational chirality model shows that a chiral C(sp)-C(sp^(3))carbon is remotely located from a blocking group.Thus,it is focused on the steric dialog between a chiral C(sp^(3))center and a remotely anchored functional group.There exist 3 energy barriers for either(R)-or(S)-C(sp)-C(sp^(3))stereogenicity in the new model.Chiral amide auxiliary was proven to be an excellent chiral auxiliary in controlling rotations of orientatiomers to give complete stereoselectivity.The asymmetric synthesis of individual orientatiomers was conducted via multistep synthesis by taking advantage of the Suzuki-Miyaura cross-coupling and Sonogashira coupling reactions.Density functional theory computational study presented optimized conformers and relative energies for individual orientatiomers.This discovery would be anticipated to result in a new stereochemistry topic and have a broad impact on chemical,biomedical,and material sciences in the future.展开更多
A new chiral aggregate-based tool for asymmetric synthesis has been developed by taking advantage of chiral aggregates of GAP(Group-Assisted Purification)reagents,N-phosphonyl imines.This tool was proven to be success...A new chiral aggregate-based tool for asymmetric synthesis has been developed by taking advantage of chiral aggregates of GAP(Group-Assisted Purification)reagents,N-phosphonyl imines.This tool was proven to be successful in the asymmetric GAP synthesis of functionalized 2,3-dihydrobenzofurans by reacting salicyl N-phosphonyl imines with dialkyl bromomalonates in various cosolvent systems.The chiral induction can be controlled by differentiating between two asymmetric directions simply by changing the ratios of cosolvents which are commonly adopted in AIE(aggregation-induced emission)systems.The formation of chiral aggregates was witnessed by a new analytical tool-aggregation-induced polarization(AIP).The present synthetic method will be broadly extended for general organic synthesis,particularly,for asymmetric synthesis and asymmetric catalysis in the future.展开更多
A new method for the synthesis of 3-thioazaspiro[4,5]trienones was developed using Pd nanoparticle catalysts,which are highly efficient,environmentally friendly and recyclable.Alkynes and thiophene phenols are effecti...A new method for the synthesis of 3-thioazaspiro[4,5]trienones was developed using Pd nanoparticle catalysts,which are highly efficient,environmentally friendly and recyclable.Alkynes and thiophene phenols are effectively cyclized by Pd/ZrO2 catalyst under visible light irradiation.The present protocol simply utilizes visible light as the safe and ecofriendly energy source,and the Pd/ZrO2 nanocomposite as photocatalyst provides a simple and practical approach to various 3-thioazaspiro[4,5]trienones in moderate conditions to high yields.展开更多
基金financial support from Robert A.Welch Foundation(D-1361-20210327,USA)the National Natural Science Foundation of China(nos.22071102 and 91956110).
文摘So far,there have been 4 methods to control chirality including the use of chiral auxiliaries,reagents,solvents,and catalysts documented in literature and textbooks.Among them,asymmetric catalysts are normally divided into homogeneous and heterogeneous catalysis.In this report,we present a new type of asymmetric control—asymmetric catalysis via chiral aggregates that would not belong to the above categories.This new strategy is represented by catalytic asymmetric dihydroxylation reaction of olefins in which chiral ligands are aggregated by taking advantage of typical aggregation-induced emission systems containing tetrahydrofuran and H_(2)O cosolvents.It was proven that the chiral induction can be enhanced from er of 78:22 to 97:3 simply by changing the ratios of these 2 cosolvents.
基金supportfrom the Robert A.Welch Foundation(D-1361-20210327,USA)from the National Natural Science Foundation ofChina(nos.22071102,91956110,22073043,and 21833002).
文摘Orientational chirality was discovered and characterized by a C(sp)-C(sp3)axis-anchored chiral center and a remotely anchored blocker.X-ray structural analysis proved that orientatiomers are stabilized by through-space functional groups,making it possible for 1 R-or S-chiral center to exhibit 3 orientational isomers simply by rotating operations.A new model system was proposed,fundamentally different from the traditional Felkin-Ahn-type or Cram-type models.In these traditional models,chiral C(sp^(3))center and blocking C(sp^(3))carbons are connected adjacently,and there exist 6 energy barriers during rotating along the C(sp^(2))-C(sp^(3))axis.In comparison,the present orientational chirality model shows that a chiral C(sp)-C(sp^(3))carbon is remotely located from a blocking group.Thus,it is focused on the steric dialog between a chiral C(sp^(3))center and a remotely anchored functional group.There exist 3 energy barriers for either(R)-or(S)-C(sp)-C(sp^(3))stereogenicity in the new model.Chiral amide auxiliary was proven to be an excellent chiral auxiliary in controlling rotations of orientatiomers to give complete stereoselectivity.The asymmetric synthesis of individual orientatiomers was conducted via multistep synthesis by taking advantage of the Suzuki-Miyaura cross-coupling and Sonogashira coupling reactions.Density functional theory computational study presented optimized conformers and relative energies for individual orientatiomers.This discovery would be anticipated to result in a new stereochemistry topic and have a broad impact on chemical,biomedical,and material sciences in the future.
基金We would like to acknowledge the financial support from the Welch Foundation(D-1361-20210327,USA)the National Natural Science Foundation of China(Nos.22071102 and 91956110).
文摘A new chiral aggregate-based tool for asymmetric synthesis has been developed by taking advantage of chiral aggregates of GAP(Group-Assisted Purification)reagents,N-phosphonyl imines.This tool was proven to be successful in the asymmetric GAP synthesis of functionalized 2,3-dihydrobenzofurans by reacting salicyl N-phosphonyl imines with dialkyl bromomalonates in various cosolvent systems.The chiral induction can be controlled by differentiating between two asymmetric directions simply by changing the ratios of cosolvents which are commonly adopted in AIE(aggregation-induced emission)systems.The formation of chiral aggregates was witnessed by a new analytical tool-aggregation-induced polarization(AIP).The present synthetic method will be broadly extended for general organic synthesis,particularly,for asymmetric synthesis and asymmetric catalysis in the future.
基金financial support from Jiangsu Planned Projects for Postdoctoral Research Funds(No.2018K293C)。
文摘A new method for the synthesis of 3-thioazaspiro[4,5]trienones was developed using Pd nanoparticle catalysts,which are highly efficient,environmentally friendly and recyclable.Alkynes and thiophene phenols are effectively cyclized by Pd/ZrO2 catalyst under visible light irradiation.The present protocol simply utilizes visible light as the safe and ecofriendly energy source,and the Pd/ZrO2 nanocomposite as photocatalyst provides a simple and practical approach to various 3-thioazaspiro[4,5]trienones in moderate conditions to high yields.
