POLYMERIZATION OF METHYL METHACRYLATE CHIRAL LIGANDS

Methyl methacrylate was anionically polymerized in the presence of chiral ligands, e. g. (+)-DDB and (-)-Sp. The polymers thus formed were optically inactive due to the instability of the helical chain for the less bulky ester group. Isotactic poly(methyl methacrylate) was given when (+)-DDB was used, whereas, a syndiotactic polymer was formed in the presence of (-)-Sp. Accordingly, two different propagation mechanisms were postulated.

Zinc Complexes of New Chiral Aminophenolate Ligands: Synthesis, Characterization and Reactivity toward Lactide

The syntheses of a library of new chiral aminophenolate bidentate O,N-type ligands HOC6H4(2-R- 4-R′)CH2N(Me)CH(Me)C6H5 [R = R′ = But, 1;R = R′ = Pent, 2;R = But, R′ = Me, 3;R = Me, R′ = But, 4;R = R′ = Me, 5] and tridentate O,N,O-type ligands HOC6H4(2,4-But)CH = NCH(R′′)C6H5 [R′′ = Me, 6;R′′ = CH2OMe, 7] are reported. These ligands were characterized by elemental analysis, nuclear magnetic resonance spectroscopy (1H & 13C), and single crystal X-ray diffraction. These ligands serve as chiral auxiliaries for inorganic chemists to design chiral metal-based complexes for asymmetric catalysis and stereoselective polymerization reactions. Three new heteroleptic zinc complexes based on these ligands have been synthesized in moderate yields via a ligand-exchange transamination reaction between homoleptic [Zn(N(SiMe3)2)2] and one equivalent of corresponding ligands to afford [L3ZnN- (SiMe3)2] (3a), [L4ZnN(SiMe3)2] (4a), and [L7ZnN(SiMe3)2] (7a). Solvent-free polymerization of raclactide at 130°C using these zinc compounds yielded atactic polylactides with Mw 10,000 g/mol and narrow polydispersity of 1.3.

Enantioselective Addition of Diethylzinc to Benzaldehyde by Catalysts of Chiral Heterocyclic Ligands

Several kinds of chiral heterocyclic ligands without hydroxyl group have been synthesized and used as catalysts for the asymmetric addition of diethylzinc to benzaldehyde. These ligands promoted the formation of (S)-1-phenylpropanols in good yields and medium to good enantioselectivities (50 similar to 86 % ee.).

The Synthesis of New Sulfur-containing Chiral Macrocyclic Ligands

Five new chiral sulfur-containing macrocyclic ligands which can be used in chiral recognition to guests have been synthesized and characterized

Axially Dissymmetric Chiral (R)-N,N′-Bis(2-hydroxy-3,5-di-tert-butyl-arylmethyl)-1,1′-binaphthalene-2,2′-diamine as Chiral Ligands in the Reaction of Diethylzinc to Aldehydes

Chiral ligand (R)-N, N'-Bis(2-hydroxy-3,5-di- tert-butyl-aryl-methyl)-1, 1'-binaphthalene-2,2'-diamine derived from the reduction of Schiff base (R)-2,2'-bis (3,5-di-tert-butyl-2-hy-droxybenzylideneamino)-1, 1'-binaphthyl with LiAIH(4) is fairly effective in the asymmetric addition reaction of diethylzinc to aldehydes by which good yields (46%-94%) of the corresponding sec-alcohols can be obtained in moderate ee (51%-79%) with R configuration for a variety of aldehydes.

Novel Chiral PNNP-Ru Complexes:Synthesis and Application in Asymmetric Transfer Hydrogenation of Ketones

The efficient catalytic systems generated in situ from RuCl2（PPh3）3 and chiral ligands N,N-bis[2-（di-o-tolylphosphino）-benzyl]cyclohexane-1,2-diamine（2） were employed for asymmetric transfer hydrogenation of aromatic ketones, giving the corresponding optically active alcohols with high activities（up to 99% conversion） and excellent enantioselectivities（up to 96% e.e.） under mild conditions. The chiral ruthenium（Ⅱ） complex （R,R）-3 has been prepared and characterized by NMR and X-ray crystallography.

Enantioselective Alternating Copolymerization of Propylene with Carbon Monoxide Using Cationic Palladium-Chiral Diphosphine Catalyst

Enantioselective alternating copolymerization of carbon monoxide with propylene was carried out using palladium catalyst modified by 1,4-3,6-dianhydro-2,5-dideoxy-2,5-bis (diphenylphosphino)-L-iditol (DDPPI). The chiral diphosphine was proved to be effective at enantioselective copolymerization. Optical rotation, elemental analysis, H-1, C-13-NMR and IR spectra showed that the copolymer was optically active, isotactic, alternating poly(1,4-ketone) structure.

Exploration of Chiral Aminophenols and Aminonaphthols with C_2-Symmetry

The exploration of C2-symmetric chiral aminophenols and aminonaphthols is described. Seven new ligands have been successfully synthesized using Mannich reaction as a key step. Four of them have C2-symmetry and their structure has been fully characterized by means of NMR and X-ray crystallography.

Synthesis and Characterization of Two Chiral Cadmium Coordination Compounds Constructed from (1S,1′S)-1,1′-(4-amino-4H-1,2,4-triazole-3,5-diyl)diethanol

Two chiral cadmium coordination compounds,（S）-[Cd（deoatrz）2 Cl2]（1）and（S）[Cd（deoatrz）2 （NO3）2]（2）（deoatrz=（1S,1 S）-1,1-（4-amino-4H-1,2,4-triazole-3,5-diyl）diethanol）,are reported.Both 1 and 2 are mononuclear,crystallizing in tetragonal P41212 chiral space group with Z=2.For1,a=11.520（3）,b=11.520（3）,c=15.175（1）,V=2013.6（1）3,Mr=527.7,Dc =1.741 g/cm 3,μ=1.386mm-1,F（000）=1064,the final GOF=1.05,R=0.0147 and wR=0.0433 for1932 observed reflections with I〉2σ（I）.For 2,a=12.201（3）,b=12.201（3）,c=15.027（4）,V=2237.1（1）3,Mr=580.8,Dc=1.725 g/cm 3,μ=1.047mm-1,F（000）=1176,the final GOF=1.00,R=0.0201 and wR=0.0415 for 2408 observed reflections with I〉2σ（I）.Compounds 1 and 2 are connected into three-dimensional supramolecular networks through hydrogen bonding interactions.

STUDIES ON STEROID PLANT-GROWTH REGULATOR 27.ENHANCED PRODUCT DIASTEREOMERIC EXCESSES IN ASYMMETRIC DIHYDROXYLATION OF THE(22E,24R)-AND THE(22E,24S)-24-ALKYL STEROIDAL UNSATURATED SIOECHAIN BY USING THE SHARPLESS IMPROVED CHIRAL LIGAND

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.

Design and synthesis of novel 1,3-diene bridged chiral atropoisomeric diphosphine ligands for asymmetric hydrogenation ofα-dehydro amino ketones

A series of novel atropisomeric diphosphine ligands termed Tan Phos were designed and synthesized,which has a smaller bite angle compared with that of other ligands such as BINAP.Tan Phos showed high reactivity and enantioselectivity in the rhodiumcatalyzed asymmetric hydrogenation ofα-dehydro amino ketones,and up 99%yield and 99%ee were obtained for a wide range of chiralα-amino ketones.

Asymmetric Reformatsky Reaction Induced by Dipeptides

For the first time, synthetic dipeptides were applied to the catalysis of asymmetric Reformatsky reaction. Review in this domain & factors influencing enantioselectivity were discussed.

Synthesis of novel chiral N,P-containing multidentate ligands and their applications in asymmetric transfer hydrogenation

Novel chiral PN_4-type multidentate aminophosphine ligands have been successfully synthesized by Schiff-base condensation of bis（o-formylphenyl）phenylphosphane and various chiral amino-sulfonamides.Their structures were fully characterized by IR,EI-MS and NMR.The catalytic systems,prepared in situ from the multidentate ligands and iridium（I） complexes,showed high activity in asymmetric transfer hydrogenation of propiophenone in 2-propanol solution,leading to corresponding optical alcohol with up to 75%ee.

Crystal Structure and Solution Behavior of a Novel Enantiopure Helical Coordination Polymer Based on Binaphthyl-bisbipyridine Ligand

An enantiopure helical coordination polymer AgPF6·（R）-3 as crystalline solid was synthesized by the self-assembly of chiral binaphthyl-based ligand（R）-6,6＇-di[6-（2,2＇-bipyridyl）]-2,2＇-diethoxyl-1,1＇-binaphthalene [（R）-3] and Ag＋ ion.The single crystal structural analysis indicates that this polymer exhibits an infinite cylindric single-stranded M-helical structure with local Λ configuration at each tetrahedral metal center.However,the extended structure is dissociated into some oligomeric fragments in solution.The 1H NMR spectra of complex AgPF6·（R）-3 show that the ligand possesses a good C2 symmetry,and the chemical shifts of the protons depend on the concentration and temperature.In addition,there are rapid dynamic exchanges among some oligonuclear fragments in the solution of AgPF6·（R）-3.

Highly enantioselective construction of CF_(3) -bearing all-carbon quaternary stereocenters: Chiral spiro-fused bisoxazoline ligands with 1,1'-binaphthyl sidearm for asymmetric Michael-type Friedel-Crafts reaction

A novel class of chiral spiro-fused bisoxazoline ligands possessing a deep chiral pocket was prepared.The developed ligands have been employed in the nickel-catalyzed highly enantioselective Michael-type Friedel-Crafts reaction, affording the products bearing a trifluoromethylated all-carbon quaternary stereocenter with moderate to excellent yields(up to 99%) and good to excellent enantioselectivies(up to> 99.9% ee). Moreover, a proposed model of chiral pocket revealed that the attack of indole from the Re-face of β-CF_(3)-β-disubstituted nitroalkene was favorable.

Enantioselective Transfer Hydrogenation of Aromatic Ketones Catalyzed by New Diaminodiphosphine Ru(Ⅱ) Complexes

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Spacial Structure of Cationic Phosphorus Ligand-Ru （Ⅱ） Halide Complexes-by DFT Study

The full-parameter geometry optimization of cationic （ S ） - BINAP - Ru （ Ⅱ ） halide complex was performed by DFT method using B3LYP, PW91 and PBE potentials with several basis sets. PW91 with 3-21G / SDD basis sets is found to be the most suitable method with consideration of both precision and efficiency. The dihedral angles （ θ ） of the binaphthyl or biphenyl with different phosphorus ligand - Ru （ Ⅱ ） halide complexes were found changing from 59.9 to 79.3 degree, while the natural bite angle （ βn ） of those complexes only changes from 87.4 to 90.3 degree. It is different from the common view of asymmetric organic chemists＇ that θ directly influences βn.

Crystal Structure of (3S, 6S, 7R, 8R)-3,6-Bis-diphenylphosphino-1,4-dioxabicyclo〔3.3.0〕octane

The title compound, C30H18O2P2, is a chiral biphospbine ligand. Itscrystal structure was determined by X-ray diffraction analysis. The crystal is or-thorhombic I space group, P212121 1 greement factor for 2326 independent reflections with (I)- In the molecu1e, two diphenylphosphino groups are in the same side of two rigidtetrahydrofuran rings and point out from each other resulting in the non-chelate charac-ter of this bidentate ligand, the title compound.

Ligand Acceleration in Chiral Lewis Acid Catalysis

Ligand-accelerated catalysis(LAC),a term originally coined by Sharpless,has been a pivotal guiding principle in the advancement of asymmetric catalysis.The discovery and understanding of LAC have not only energized the enhancement of established catalytic asymmetric transformations but also ignited the creation of novel ones.In this review,we have curated a selection of illustrative examples,delving into the profound influence that chiral ligands exert on the acceleration of Lewis acid-promoted reactions,encompassing both thermally induced and photochemical processes.The impact of a chiral ligand on various facets,including solubility,aggregation state,geometry,Lewis acidity,and photophysical properties of metal salts,has been identified as crucial determinants.Moreover,the covalent and noncovalent interactions between ligands and substrates,the creation of chiral pockets by chiral ligands and metals,as well as the alterations in the physical and chemical properties of substrates induced by Lewis acid coordination,also play significant roles.Notably,the utilization of ligandaccelerated asymmetric Lewis acid catalysis in photoreactions presents an efficient approach for addressing the challenges associated with stereocontrol.We anticipate that this review will inspire researchers to pay more attention to the role of ligands and aid in the development of new efficient ligands and asymmetric reactions.