A comparison of the asymmetric hydrogenation catalyzed by rhodium complexes containing chiral ligands with a binaphthyl unit and those with a 5,5′,6,6′,7,7′,8,8′-octahydro-binaphthyl unit

The chiral ligands H₈–BINAPO and H₈–BDPAB were synthesized by reacting chlorodiphenylphosphine with H₈–BINOL and H₈–BINAM, respectively. Applications of these ligands in the Rh-catalyzed enantioselective hydrogenation of a variety of (Z)-acetamido-3-arylacrylic acid methyl esters provided chiral amino acid derivatives with good to excellent enantioselectivities (H₈–BINAPO: up to 84.0% e.e.; H₈–BDPAB: up to 97.1% e.e.). In the hydrogenation of acetamidoacrylic acid, 99% e.e. was obtained when a [Rh(H₈–BDPAB)]⁺ catalyst was used. The catalytic activities and enantioselectivities of [Rh(H₈–BINAPO)]⁺ and [Rh(H₈–BDPAB)]⁺ are substantially better than those obtained with the corresponding rhodium catalysts containing BINAPO (up to 64% e.e.) and BDPAB (up to 92.6% e.e.).     

Synthesis of novel N,P chiral ligands for palladium-catalyzed asymmetric allylations: the effect of binaphthyl backbone on the enantioselectivity

A series of novel chiral aminophosphine ligands with a 5,5,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthyl backbone (H₈-MAPs) have been synthesized. The application of these ligands in asymmetric allylic substitutions was examined and higher enantioselectivity was observed than that by using the parent ligand (MAP). Under the optimized conditions, the allylation product can be obtained in up to 90.9% ee with H₈-MAP having 3,5-xylyls as chiral inducer. The dramatic effect of the binaphthyl backbone on the enantioselectivity of the reaction can be attributed to the change of the bite angle in H₈-MAPs/Pd complexes.     

Chiral anionic layers in tartramide spiroborate salts and variable solvation for [NR4][B(TarNH2)2] (R = Et,Pr or Bu)

The spiroborate anion, namely, 2,3,7,8‐tetracarboxamido‐1,4,6,9‐tetraoxa‐5λ⁴‐boraspiro[4.4]nonane, [B(TarNH₂)₂]^?, derived from the diol l ‐tartramide TarNH₂, [CH(O)(CONH₂)]₂, shows a novel self‐assembly into two‐dimensional (2D) layer structures in its salts with alkylammonium cations, [NR₄]⁺ (R = Et, Pr and Bu), and sparteinium, [HSpa]⁺, in which the cations and anions are segregated. The structures of four such salts are reported, namely, the tetrapropylazanium salt, C₁₂H₂₈N⁺·C₈H₁₂BN₄O₈^?, the tetraethylazanium salt hydrate, C₈H₂₀N⁺·C₈H₁₂BN₄O₈^?·6.375H₂O, the tetrabutylazanium salt as the ethanol monosolvate hemihydrate, C₁₆H₃₆N⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH·0.5H₂O, and the sparteinium (7‐aza‐15‐azoniatetracyclo[7.7.1.0^2,7.0^10,15]heptadecane) salt as the ethanol monosolvate, C₁₅H₂₇N₂⁺·C₈H₁₂BN₄O₈^?·C₂H₅OH. The 2D anion layers have preserved intermolecular hydrogen bonding between the amide groups and a typical metric repeat of around 10 × 15 Å. The constraint of matching the interfacial area organizes the cations into quite different solvated arrangements, i.e. the [NEt₄] salt is highly hydrated with around 6.5H₂O per cation, the [NPr₄] salt apparently has a good metric match to the anion layer and is unsolvated, whilst the [NBu₄] salt is intermediate and has EtOH and H₂O in its cation layer, which is similar to the arrangement for the chiral [HSpa]⁺ cation. This family of salts shows highly organized chiral space and offers potential for the resolution of both chiral cations and neutral chiral solvent molecules.     

Tris(2,2′‐bipyridine)iron(II) bis(1,1,3,3‐tetracyano‐2‐ethoxypropenide) dihydrate: chiral hydrogen‐bonded frameworks interpenetrate in three dimensions

In the title compound, [Fe(C₁₀H₈N₂)₃](C₉H₅N₄O)₂·2H₂O, the chiral cations lie across twofold rotation axes in the space group C2/c. The anions and the water molecules are linked by two independent O—H...N hydrogen bonds to form C₂²(8) chains, and these chains are linked by the cations via C—H...N and C—H...O hydrogen bonds to form two interpenetrating three‐dimensional frameworks, each of which contains only one enantiomeric form of the chiral cation.     

Gold‐Decorated Chiral Macroporous Films by the Self‐Assembly of Functionalised Block Copolymers

We describe a new and very versatile method to place chosen chemical functionalities at the edge of the pores of macroporous materials. The method is based on the synthesis and self‐assembly of inorganic block copolymers (BCPs) having chiral rigid segments bearing controllable quantities of randomly distributed functional groups. The synthesis of a series of optically active block copolyphosphazenes (PP) with the general formula [N?P(R‐O₂C₂₀H₁₂)_0.9(FG)_0.2]_n‐b‐[N?PMePh]_m (FG=‐OC₅H₄N ( 6 ), ‐NC₄H₈S ( 7 ), and ‐NC₄H₈O ( 8 )), was accomplished by the sequential living cationic polycondensation of N‐silylphosphoranimines, using the mono‐end‐capped initiator [Ph₃P?N?PCl₃][Cl] ( 3 ). The self‐assembly of the phosphazene BCPs 6 – 8 led to chiral porous films. The functionality present on those polymers affected their self‐assembly behaviour resulting in the formation of pores of different diameters (D_n=111 ( 6 ), 53 ( 7 ) and 77 nm ( 8 )). The specific functionalisation of the pores was proven by decorating the films with gold nanoparticles (AuNPs). Thus, the BCPs 6 and 7 , having pyridine and thiomorpholine groups, respectively, were treated with HAuCl₄, followed by reduction with NaBH₄, yielding a new type of block copolyphosphazenes, which self‐assembled into chiral porous films specifically decorated with AuNPs at the edge of the pores.     

The 1:1 adduct of 5‐methylbenzene‐1,3‐diol (orcin) and 1,4‐di­aza­bicyclo­[2.2.2]­octane

In the title adduct, C₆H₁₂N₂·C₇H₈O₂, the orcin and 1,4‐di­aza­bi­cyclo­[2.2.2]­octane moieties are held together by O—H⋯N hydrogen bonds. One‐dimensional chiral hydrogen‐bonded chains are formed along the b axis. Neighbouring chains are held together principally by van der Waals interactions and are interrelated by translation, resulting in a chiral layer.     

The Allylic Oxidation of Geraniol Catalyzed by Cytochrome P-450Cath., Proceeding with retention of configuration

Incubation of the geraniols (R)-(8-²H₁)[8-³H₁]- 1 and (S)-(8-²H₁)[8-³H₁]- 1 with microsomal cytochrome P-450_Cath. from the subtropical plant Catharanthus roseus (L.)G. DON resulted in the formation of the chiral 8-hydroxygeraniols (S)-(8-²H₁)[8-³H₁]- 2 and (R)-(8-²H₁)[8-³H₁]- 2 . Their absolute configuration was assigned on the basis of the ¹H-decoupled ³H-NMR Spectra of the corresponding dicamphanates (S)-(8-²H₁)[8-³H₁]- 9 and (R)-(8-²H₁)[8-³H₁]- 9 , of which the configurations are established in relation to the synthetic reference samples. The results clearly indicate retention of configuration during the allylic oxidation of 1 .     

A chiral furocoumarin

The furocoumarin 1,2‐di­hydro‐2‐(1,2‐di­hydroxy­prop‐2‐yl)‐8H‐furo­[2,3‐h]­benzo­pyran‐8‐one crystallizes from methanol–water as the monohydrate C₁₄H₁₄O₅·H₂O. Both chiral centers have the S configuration. Both OH groups and both H atoms of the water mol­ecule form intermolecular hydrogen bonds with O?O distances in the range 2.7686 (18)–2.8717 (18) Å.     

The crystal structures of chiral (<Emphasis Type="Italic">R</Emphasis>/<Emphasis Type="Italic">S</Emphasis>) (C<Subscript>8</Subscript>H<Subscript>11</Subscript>N)<Subscript>2</Subscript>·CuCl<Subscript>2</Subscript>

Two opposite configuration (R/S) of chiral complexes (C₈H₁₁N)₂·CuCl₂ were obtained from the reaction of chiral d(+)/l(−)-α-ethylphenyl amine with copper chloride (II) in dry ethanol. The crystal structures of 1a and 1b were characterized by IR, elemental analysis and X-ray crystallography.     

Synthesis of diphosphite ligands derived from glucopyranoside and their application in the Cu-catalyzed asymmetric 1,4-addition of organozinc to enones

Novel chiral diphosphite ligands derived from glucopyranoside and H₈-binaphthol were synthesized, and successfully employed in the Cu-catalyzed asymmetric 1,4-addition of organozinc reagents dimethylzinc, diethylzinc, and diphenylzinc to cyclic and acyclic enones with up to 96% ee. The stereochemically matched combination of d-glucopyranoside backbone and (R)-H₈-binaphthyl in the ligand 2,4-bis{[(R)-1,1′-H₈-binaphthyl-2,2′-diyl] phosphite}-phenyl 3,6-anhydro-β-d-glucopyranoside was essential for inducing high enantioselectivity. A significant dependence of stereoselectivity on the type of enones and the ring size of cyclic enones was observed. Moreover, the sense of the enantiodiscrimination of the products was mainly determined by the configuration of the H₈-binaphthyl moieties.     

A selector/selectand molecular complex for the study of enantiodiscriminative processes

The structure of the molecular complex between the chiral selector (+)1-(3-allylpropyl)-(5R,8S,10R)-N,N-diethyl-N′-[6-methyl ergolin-8-yl]urea, C₂₃H₃₃N₄O, (allyl-terguride) and the HPLC more retained (S)-enantiomer of dansyl-tryptophan, C₂₃H₂₃N₃O₄S, has been determined. It is a part of the study on the chiral recognition mechanism of ergot alkaloids, when used in chiral stationary phases (CSPs) for the separation of racemic mixture of organic acids by liquid chromatographic methods. At the pH of crystallization conditions, which mimic those corresponding to the best enantiodiscriminative activity, each molecule of (S)-dansyl-tryptophan is locked to a molecule of allyl-terguride by hydrogen bonds and by C–H···π edge-to-face interactions.     

Molecular Complexes for the Study of Enantiodiscriminative Processes

The structure of the molecular complex between the chiral selector (+)1-(3-allylpropyl)-(5R,8S,10R)-N,N-diethyl-N-[6-methylergolin-8-yl]urea, C₂₃H₃₃N₄O, (allyl-terguride) and the more retained (S) isomer of dansyl-serine, C₁₅H₁₉N₂O₅S, has been determined. It is part of a study on the chiral recognition mechanism of ergot alkaloids, when used in chiral stationary phases for the separation of racemic mixture of organic acids by liquid chromatographic methods. At the pH of the crystallization conditions, which mimick those corresponding to the best enantiodiscriminative activity, each molecule of (S)-dansyl-serine is locked by hydrogen bonds between two translation related molecules of allyl-terguride forming a infinite chains in a 1:1 molecular ratio.     

A three‐dimensional homochiral metal–organic framework constructed from manganese(II) with S‐carboxymethyl‐N‐(p‐tosyl)‐l‐cysteine and 4,4′‐bipyridine

In the chiral polymeric title compound, poly[aqua(4,4′‐bipyridine)[μ₃‐S‐carboxylatomethyl‐N‐(p‐tosyl)‐l ‐cysteinato]manganese(II)], [Mn(C₁₂H₁₃NO₆S₂)(C₁₀H₈N₂)(H₂O)]_n, the Mn^II ion is coordinated in a distorted octahedral geometry by one water molecule, three carboxylate O atoms from three S‐carboxyatomethyl‐N‐(p‐tosyl)‐l ‐cysteinate (Ts‐cmc) ligands and two N atoms from two 4,4′‐bipyridine molecules. Each Ts‐cmc ligand behaves as a chiral μ₃‐linker connecting three Mn^II ions. The two‐dimensional frameworks thus formed are further connected by 4,4′‐bipyridine ligands into a three‐dimensional homochiral metal–organic framework. This is a rare case of a homochiral metal–organic framework with a flexible chiral ligand as linker, and this result demonstrates the important role of noncovalent interactions in stabilizing such assemblies.     

The crystal structures of chiral (R/S) (C8H11N)2·Cu(OAc)2

The two title chiral complexes (R/S) (C₈H₁₁N)₂·Cu(OAc)₂ were synthesized by the reaction of chiral d(+)/l(?)-??-ethylphenyl amine with copper(II) acetate monohydrate in dry ethanol. The crystal structures of 1a and 1b were obtained and determined by X-ray crystallography.     

Poly[[trans‐diaquabis(μ2‐biphenyl‐2,2′‐dicarboxylato)bis(μ2‐4,4′‐bipyridine)dicobalt(II)] biphenyl‐2,2′‐dicarboxylic acid disolvate]

In the title compound, {[Co₂(C₁₄H₈O₄)₂(C₁₀H₈N₂)₂(H₂O)₂]·2C₁₄H₁₀O₄}_n, each Co^II ion is six‐coordinate in a slightly distorted octahedral geometry. Both Co^II ions are located on twofold axes. One is surrounded by two O atoms from two biphenyl‐2,2′‐dicarboxylate (dpa) dianions, two N atoms from two 4,4′‐bipyridine (bpy) ligands and two water molecules, while the second is surrounded by four O atoms from two dpa dianions and two N atoms from two bpy ligands. The coordinated dpa dianion functions as a κ³‐bridge between the two Co^II ions. One carboxylate group of a dpa dianion bridges two adjacent Co^II ions, and one O atom of the other carboxylate group also chelates to a Co^II ion. The Co^II ions are bridged by dpa dianions and bpy ligands to form a chiral sheet. There are several strong intermolecular hydrogen bonds between the H₂dpa solvent molecule and the chiral sheet, which result in a sandwich structure.     

Synthesis and Stereochemical Assignment of Crypto‐Optically Active 2H6‐Neopentane

The determination of the absolute configuration of chiral molecules is at the heart of asymmetric synthesis. Here we probe the spectroscopic limits for chiral discrimination with NMR spectroscopy in chiral aligned media and with vibrational circular dichroism spectroscopy of the sixfold‐deuterated chiral neopentane. The study of this compound presents formidable challenges since its stereogenicity is only due to small mass differences. For this purpose, we selectively prepared both enantiomers of ²H₆‐ 1 through a concise synthesis utilizing multifunctional intermediates. While NMR spectroscopy in chiral aligned media could be used to characterize the precursors to ²H₆‐ 1 , the final assignment could only be accomplished with VCD spectroscopy, despite the fleetingly small dichroic properties of 1 . Both enantiomers were assigned by matching the VCD spectra with those computed with density functional theory.     

新法合成手性磷酸锌钠

对合成手性磷酸锌钠(NaZnPO₄·H₂O) (CZP)的新方法进行了研究,用Na₃PO₄·12H₂Oand ZnSO₄·7H₂O作为起始原料,聚乙二醇-400（PEG-400）为表面活性剂,通过一步低热固相反应得到了手性磷酸锌钠。用TG/DTG,XRD, TEM 及 SEM表征了产物。实验结果表明,Na₃PO₄·12H₂O与ZnSO₄·7H₂O的配比采用不同的p/Zn比（0.9～1.15）,在60 ℃下陈化不同的时间(2.0～8.0 h) 所得到的NaZnPO₄·H₂O,除了结晶度稍为不同之外,晶体的手性结构是一样的。对照实验的结果显示陈化温度及阴离子调控着NaZnPO₄·H₂O的对映体形态。即,若以ZnSO₄·7H₂O或Zn(NO₃)₂·6H₂O为锌源,当反应混合物在60 ^oC陈化时,生成产物的结构是空间群为 P6₁22 的第一种手性结构,当反应混合物在室温陈化时,生成产物的结构则是空间群为 P6₅22 的第二种手性结构。     

中心金属或配体刚性调控的α-酮酸酯对硝基烯的不对称共轭加成

通过手性二胺配体与Cu或Ni络合合成了手性金属催化剂,并将其应用于α-酮酸酯对硝基烯的不对称共轭加成反应中,发展了通过改变中心金属或调节配体刚性实现反应对映选择性反转的策略.使用同一手性二胺配体(1S,1'S)-1,1'-联异吲哚啉,与不同的金属前体(Cu(OAc)2·H2O与Ni(OAc)2·4H2O)络合,可以高选择性地得到绝对构型相反的共轭加成产物(ee值高达94%与93%).同样,使用同一金属前体Cu(OAc)2·H2O,与同一手性源出发合成的两种刚性不同的二胺配体络合,也可以在这个反应中实现产物绝对构型的反转(ee值高达94%与94%).     

Phosphoramidites of Chiral (Rp)-and (Sp)-Configurated d(T[P-18O]-A): Synthesis,Configurational Assignment,and Use as Dimer Blocks in Oligonucleotide Synthesis

The N,N-diisopropylphosphoramidites 10a and 10b of appropriately protected chiral diastereoisomers of d(T[P-¹⁸O]-A) ( 8a and 8b , resp.), chiral by virtue of the isotope ¹⁸O at the P-atom, have been synthesized. The ¹⁸O-isotope was incorporated by oxidation of the phosphite triester 3 with H₂[¹⁸O]/I₂. Separation of the diastereoisomers was accomplished by flash chromatography of the O-3′-deprotected phosphate triesters 5a/b . The absolute configuration at the chiral P-atom was deduced from the methylation products of the fully deprotected diastereoisomers 8a and 8b . Phosphinylation of 5a and 5b yielded the configurationally pure phosphoramidites 10a and 10b , respectively, which were then employed in solid-phase synthesis to yield the self-complementary oligomers d(G-A-G-T-(R_p)-[P-¹⁸O]-A-C-T-C) ( 13 ) and d(G-A-G-T-(S_P)-[P-¹⁸O]-A-C-T-C) ( 14 ), respectively.     

Asymmetric synthesis of differentially protected α-alkyl succinates

The alkylation of the chiral iron acyls [(η⁵-C₅H₅)Fe(CO)(PPh₃)COCH₂R] (R = H, Me, n-Pr, n-Bu, i-Bu, n-C₅H₁₁) with t-butyl bromoacetate takes place highly stereoselectively to provide a series of novel iron succinoyl complexes, which on oxidative decomplexation lead directly to chiral α-alkyl succinates.