A Dispensable Methoxy Group? Phenyl Fencholate as a Chiral Modifier of n‐Butyllithium

Phenyl fenchol forms a 3:1 aggregate with n-butyllithium (3-BuLi), showing unique lithium-HC agostic interactions both in toluene solution (1H,7Li-HOESY) and in the solid state (X-ray analysis). Although methoxy-lithium coordination is characteristic for many mixed aggregates of anisyl fencholates with n-butyllithium, endo-methyl coordination to lithium ions compensates for the missing methoxy groups in 3-BuLi. This gives rise to a different orientation of the fenchane moiety, encapsulating and chirally modifying the butylide unit.     

Synthesis, Crystal Structure and Magnetic Properties of a New Zn(Ⅱ)-Nitronyl Nitroxide Complex

A new complex [Zn(NIT-1'-MeBzIm)Cl2(H2O)] (NIT-1'-MeBzIm = 2-{2'-[(1'-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide) has been prepared and structurally characterized by X-ray diffraction method. Crystal data: monoclinic, space group P21/n, Z = 4, C15H21Cl2N4O3Zn, Mr = 441.63, a = 7.2225(10), b = 30.849(4), c = 8.8758(13) (A), β= 103.904(2)°, V = 1919.6(5) A3, Dc = 1.528 g/cm3, μ(MoKα) = 1.579 mm-1, F(000) = 908, R = 0.0436 and wR = 0.1029 for 2456 observed reflections with Ⅰ> 2σ(Ⅰ). X-ray analysis reveals that the Zn(Ⅱ) ion is four-coordinated with a distorted tetrahedron. There also exist H-bonds, π-π piling interactions and weak intermolecular contacts between the NO groups which form a mutual stagger 3-D network configuration. Magnetic investigation reveals that there exists intermolecular antiferro- and ferromagnetic interactions in the title complex.     

Synthesis,Crystal Structure and Magnetic Properties of a New Zn（Ⅱ）-Nitronyl Nitroxide Complex

A new complex [Zn（NIT-1′-MeBzlm）Cl2（H2O）] （NIT-1′-MeBzlm = 2-{2′-[（1′- methyl）benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide） has been prepared and structurally characterized by X-ray diffraction method. Crystal data： monoclinic, space group P21/n, Z = 4, C15H21Cl2N4O3Zn, Mr = 441.63, a = 7.2225（10）, b = 30.849（4）, c = 8.8758（13）A, β = 103.904（2）°, V = 1919.6（5）A^3, Dc = 1.528 g/cm^3, μ（MoKα） = 1.579 mm^-1, F（000） = 908, R = 0.0436 and wR = 0.1029 for 2456 observed reflections with I〉 2σ（I）. X-ray analysis reveals that the Zn（Ⅱ） ion is four-coordinated with a distorted tetrahedron. There also exist H-bonds, π-π piling interactions and weak intermolecular contacts between the NO groups which form a mutual stagger 3-D network configuration. Magnetic investigation reveals that there exists intermolecular antiferro- and ferromagnetic interactions in the title complex.     

Cyclization Reaction of α-Triazolyl-α, β-unsaturated Ketones with Phenyl hydrazine

InourpreviousworkwehavereportedthestudiesonthereactionofvinyItriazolcderivativeswithhydroxylamine,andfOundthatcycloadditiontookp1aceandthenewheterocycliccompoundsl,2-oxazocyclopentaneshavingplant-growthregulatingactivitywereobtainedl,2.InordertosynthesizenewheterocycliccompoundsandtosearchfOrnewcompoundshavingbioactivity,thereactionofa-triazolyl-a,ll-unsaturatedketones(Z)-or(E)-4,4-dimethyl-1-aryl-2-(l,2,4-triazol-l-yl)-l-penten-3-onesI.-bwithphenylhydrazinewasstudied.Theresultshowedthatcycl…     

A Heteroleptic Dirhodium Catalyst for Asymmetric Cyclopropanation with α-Stannyl α-Diazoacetate. “Stereoretentive” Stille Coupling with Formation of Chiral Quarternary Carbon Centers

The heteroleptic dirhodium paddlewheel catalyst 7 with a chiral carboxylate/acetamidate ligand sphere is uniquely effective in asymmetric [2+1] cycloadditions with α-diazo-α-trimethylstannyl (silyl, germyl) acetate. Originally discovered as a trace impurity in a sample of the homoleptic parent complex [Rh₂((R)-TPCP)₄] ( 5 ), it is shown that the protic acetamidate ligand is quintessential for rendering 7 highly enantioselective. The -NH group is thought to lock the ensuing metal carbene in place via interligand hydrogen bonding. The resulting stannylated cyclopropanes undergo “stereoretentive” cross coupling, which shows for the first time that even chiral quarternary carbon centers can be made by the Stille–Migita reaction.     

Intramolecular Induction of Asymmetric Darzen's Condensation of Aldehydes with Chiral α-Chloroacetates

Inconvergentwithourinterestintheasymmetricsynthesisofnaturalproducts,intramolecularinductionofasymmetricDarzen'scondensationlofaldehydeswithQchloroacetatesofchiralalcoholswasstudies,asshowninScheme1.Scheme1.R*OH CICH,COCI~CICH,COOR*i(-)-menthol(450%)3( )-Jsomenthoi(i56%)5(-)-8-phenylmenthoi(74%)2( )-neomenthol(147%)4( )-f6nchol(478%)6(-)-8-11-naphthylmenthoi(99%)I-henumbersintileparenthesisilldicatedthece%oftilecorrcspondillgmethy13-pllcn}lgl}'cidatcobtainedh\'trallscstcrltiationBenza…     

Enantio- and Diastereoselective Synthesis of Chiral Tetrasubstituted α-Amino Allenoates Bearing a Vicinal All-Carbon Quaternary Stereocenter with Dual-Copper-Catalysis

The skeletons of chiral tetrasubstituted allenes bearing a vicinal all-carbon quaternary stereocenter are of importance but still challenging to synthesize. Herein, we report enantio- and diastereoselective γ-additions of 1-alkynyl ketimines with dual-copper-catalysis under mild conditions, affording chiral tetrasubstituted α-amino allenoates bearing a vicinal all-carbon quaternary stereocenter in high yields (up to 99 % yield) with excellent enantioselectivities (up to 99 % ee) and diastereoselectivities (up to >20 : 1 dr). Importantly, the stereodivergent synthesis of the products was realized by the asymmetric γ-addition reaction and the Grignard reagent promoted epimerization. Moreover, the dual-copper-catalyzed γ-addition reactions were smoothly applied to a gram-scale reaction and adopted to introduce chiral tetrasubstituted allenyl moieties into bioactive molecules. Mechanistic experiments and density functional theory (DFT) calculations demonstrated that the asymmetric γ-addition reactions were catalyzed by double chiral copper catalysts.     

Chiral Phosphoric Acid Dual-Function Catalysis: Asymmetric Allylation with α-Vinyl Allylboron Reagents

We report a dual function asymmetric catalysis by a chiral phosphoric acid catalyst that controls both enantioselective addition of an achiral α-vinyl allylboronate to aldehydes and pseudo-axial orientation of the α-vinyl group in the transition state. The reaction produces dienyl homoallylic alcohols with high Z-selectivities and enantioselectivities. Computational studies revealed that minimization of steric interactions between the alkyl groups of the diol on boron and the chiral phosphoric acid catalyst influence the orientation of α-vinyl substituent of the allylboronate reagent to occupy a pseudo-axial position in the transition state.     

Asymmetric Synthesis of Aryl 2-Piperidyl Methanols from a Chiral α-Aminonitrile Precursor

Synthesis of enantiomerically pure phenyl 2-piperidyl methanols from a convenient chiral α-aminonitrile 1 is described. Reaction with aldehydes of the anion generated from 1 leads to threo (αR, 2R) products, whereas treatment of 1 with organolithium reagents affords erythro (αR, 2S) compounds.     

Chiral N-heterocyclic carbene catalyzed annulation of α,β-unsaturated aldehydes with 1,3-dicarbonyls

Chiral N-heterocyclic carbene catalyzed annulations of ynals and enals with 1,3-dicarbonyls have been described. The two reactions provided direct and efficient methods for enantioselective synthesis of functionalized dihydropyranones. Comparatively, the reactions starting from ynals were atom-economical; furthermore the reactions of enals demonstrated broader substrate compatibility.     

Chiral azo compounds: enantioselective synthesis and transformations into β-amino alcohols and α-amino acids with a quaternary stereocenter

Taking advantage of radical carboaminations producing azo compounds, a new chemo-enzymatic approach to enantiomerically enriched azo alcohols, β-amino alcohols and non-natural (aromatic) amino acids with a quaternary stereocenter is reported.     

Asymmetric Reduction of Chiral Titanates of α-Keto Aromatic Acids with Lithium Dialkyl Amides

Asymmetric reduction of titanates of α-keto aromatic acids with chiral alcohol ligands by lithium dialkyl amides yielded the acids' corresponding mandelic acids in 20.1 to 43.3%ee.     

Chiral phosphoric acid catalyzed aza-Friedel-Crafts alkylation of indoles with cyclic aryl α-ketimino esters

A highly enantioselective aza-Friedel-Crafts alkylation of indoles with cyclic aryl α-ketimino esters catalyzed by a chiral phosphoric acid has been developed, the corresponding α,α-disubstituted unnatural α-amino ester derivatives were obtained in moderate to high yields (67–85%) with high enantioselectivities (up to 93% ee) under mild reaction conditions.     

A Novel Binuclear Cu（Ⅱ） Complex with Nitroxide Radicals Exhibiting Ferromagnetic Interactions

A new binuclear Cu(Ⅱ) complex with nitronyl nitroxide radicals [Cu(NIT3Py)2Cl2]2(NIT3Py = 2-(3'-pyridinyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) has been synthesized and structurally characterized by X-ray diffraction analysis.It crystallizes in monoclinic,space group C2/c with a = 38.483(4),b = 7.2450(8),c = 27.559(3) ,β = 134.0180(10)°,V = 5525.6(10) 3,C48H64Cl4Cu2N12O8,Mr = 1206.00,Z = 4,Dc = 1.450 g/cm3,μ(MoKα) = 1.025 mm-1,F(000) = 2504,S = 1.066,the final R = 0.0471 and wR = 0.1121 for 3286 observed reflections(I > 2σ(I)).The title complex consists of centrosymmetric dinuclear units [Cu(NIT3Py)2Cl2]2,in which the copper ions are square-pyramidally coordinated by two pyridyl nitrogen atoms of two radical ligands and three chlorine anions,two of which bridge the copper ions.The magnetic measurements show ferromagnetic interactions between the copper ions and the radical ligands.     

Communication: Conformation state diagram of polypeptides: a chain length induced α-β transition

By using a generic coarse grained polypeptide model, we perform multicanonical molecular dynamics simulations for determining the equilibrium conformation state diagram of a single homopolypeptide chain as a function of the chain length and temperature. The state diagram highlights the thermal regimes of stability for various conformational patterns in polypeptides, including swollen, random and collapsed coils, globular structures, extended and bended α helices, and compact β bundles. Remarkably, at low temperatures we observe a sharp transition from extended α helix to compact β bundles as the chain length increases. This finding indicates that the chain length is one of the intrisic factors that can trigger α-β transformations in a broad class of polypeptides.     

Palladium-Catalyzed Cross-Coupling Reaction of Phenyl Fluoroalkanesulfonates with Allyltributyltin

Transition metal-catalyzed cross-coupling reaction is an efficient method of carbon-carbon bond formation.e.g.palladium-catalyzed reaction for vinyl triflates with orga-notin reagents provides a good example of this kind.The authors and othershave shown that palladium could insert into the carbon-oxygen bond of phenyl fluoroal-kanesulfonate(ArOSO_2R_f1)via oxidative addition.Very recently,the transmetallationof this arylpalladium(Ⅱ)species with organozinc reagents giving the correspondingalkylbenzenes has also been reported.Herein we wish to present another novel cross--coupling reaction of phenyl fluoroalkanesulfonates(1)with an organometallic reagent,allyltributyltin(2)in the presence of catalytic amounts of tetrakis(triphenylphos-phine)-palladium to give the corresponding allyl benzenes(3)in good yields.     

A Novel Complex of Na（I）-Nitronyl Nitroxide [Na（NIT- 1＇-MeBzIm）3]ClO4： Synthesis and Crystal Structure

A novel complex [Na（NIT-1＇-MeBzIm）3]ClO4 （NIT-1＇-MeBzIm = 2-{2＇-[（1＇- methyl）benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide） has been prepared and structurally characterized by elemental analysis, IR spectra and X-ray diffraction methods. The title complex crystallizes in trigonal, space group P3 and Z = 2. Crystal data： C45H57ClN12NaO10, Mr = 984.47, a = 13.9411（8）, b = 13.9411（8）, c = 14.8622（16） A, γ= 120°, V= 2501.5（3） A^3, Dc = 1.307 g/cm^3, μ（MoKα） = 0.152 mm^-1, F（000） = 1038, R = 0.0637 and wR = 0.1813 for 1957 observed reflections with I 〉 2σ（I）. X-ray analysis reveals that the Na（I） ion is six-coordinated with three NIT-1＇-MeBzlm radicals. As we know, three radicals coordinating to the Na（I） ion in the main group by a chelate way is the first example. The Na（I） ion resides in a distorted octahedron with a facial configuration. Meanwhile, the intermolecular weak interactions result in a 2-D double layer conformation where the uncoordinated perchlorate anions are inserted in the packing space and take part in the H-bond interactions, and each complex is connected with six neighboring complexes and three perchlorate anions.     

Cu(I)/Chiral Bisoxazoline-Catalyzed Enantioselective Doyle-Kirmse Reaction of Allenyl Sulfides with α-Diazoesters

Herein, a Cu(I)-catalyzed enantioselective Doyle-Kirmse reaction of allenyl sulfides and α-diazoesters is reported, which provides an efficient synthetic route to enantio-enriched chiral tertiary homopropargylic sulfides. This reaction features high enantioselectivities (up to 96 % ee) and good functional group tolerance. The alkyl substituted α-diazoester has also been demonstrated as the efficient substrates in the asymmetric Doyle-Kirmse reaction. Mechanistic studies, including kinetic experiments, were conducted to gain insights into the details of the reaction pathway. The potential synthetic utility of this protocol has also been demonstrated.     

Chiral Separation of Erythromycin as a New Chiral Selector on CE

Erythromycin as a new chiral selector was first used for chrial separation of four derivatives of biphenyldimethylester enantiomers on CE.The influence of pH,the chiral selector concentration and organic modifiers were preliminarily studied.Experiments show that the erythromycin as chiral selector is useful to CE.     

Synthesis of a new,C 2 Symmetric α,α - Bis-(Carboxymethyl) Substituted Nitroxide

The novel, diastereomeric meso- (cis) and (±)- (trans) nitroxides 2,5-dicarboxymethyl-2,5-dimethylpyrrolidine-1-oxyl have been synthesized via a dienolate based strategy. Both optically pure enantiomers of the C ₂ symmetric trans diastereomer have been obtained via resolution of the corresponding amine with dibenzoyltartaric acid.