Asymmetric oxidation of sulfides catalyzed by chiral (salen)Mn(III) complexes with a pyrrolidine backbone

Catalytic properties of a series of chiral (pyrrolidine salen)Mn(III) complexes for asymmetric oxidation of aryl methyl sulfides were evaluated. Moderate activity, good chemical selectivity and low enantioselectivity were attained with iodosylbenzene as a terminal oxidant. Enantioselectivity of sulfide oxidation was affected slightly by polar solvent and the sulfoxidation carried out in THF for thioanisole and in CH₃CO₂Et for electron‐deficient sulfides gave better enatioselctivities. The addition of the donor ligand PPNO (4‐phenylpyridine N‐oxide) or MNO (trimethylamine N‐oxide) only has a minor positive effect on the enantioselectivity. Also explored was the steric effect of the N_aza‐substituent in the backbone of (pyrrolidine salen)Mn(III) complexes on the enantioselectivity of sulfide oxidation. The sulfides' access pathway is discussed based on the catalytic results. Copyright © 2006 John Wiley & Sons, Ltd.     

Asymmetric synthesis of (S,R)- and (R,R)-methiin stereoisomers

Abstract

An asymmetric synthesis of (+)- and (–)-methiine (S-methyl-(R)-cysteine sulfoxide) diastereomers has been developed. These natural sulfur compounds were isolated from a variety of Brassica vegetables. As the starting compound, (R)-cysteine was used, which was methylated to form (R)-S-methylcysteine. Then the oxidation of S-methylcysteine with tert-butyl hydroperoxide catalyzed by the chiral tetra(isopropylate)titanium/(S)- or (R)-Binol complex led to the formation of (1?R,2S)-(+)- or (1?R,2R)-(–)-methiin stereomers.     

New chiral Schiff bases derived from (+)- and (−)-α-pinenes in the metal complex catalyzed asymmetric oxidation of sulfides

New chiral Schiff bases were derived from (+)- and (−)-α-pinenes for the first time. Coordinated to vanadium ions, they can be used as ligands in catalytic oxidation of sulfides into chiral sulfoxides. Conditions for the asymmetric oxidation of thioanisole to methyl phenyl sulfoxide in optical purity up to 32% were found. Variation of substituents in the ligand has a significant effect not only on enantioselectivity of the reaction, but also on absolute configuration of the sulfoxide formed. Dedicated to Academician G. A. Tolstikov in honor of his 75th anniversary. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 105–113, January, 2008.     

Asymmetric oxidation of sulfides with H2O2 catalyzed by titanium complexes of Schiff bases bearing a dicumenyl salicylidenyl unit

The sterically hindered Schiff bases (L³–L⁵), prepared from 3,5‐dicumenyl salicylaldehyde and chiral amino alcohols, were used in combination with Ti(OiPr)₄ for asymmetric oxidation of aryl methyl sulfides with H₂O₂ as terminal oxidant. Among the ligands L³–L⁵, L⁴ with a tert‐butyl group in the chiral carbon of the amino alcohol moiety gave the best result with 89% yield and 73% ee for the sulfoxidation of thioanisole under optimal conditions [with 1 mol% of Ti(OiPr)₄ in a molar ratio of 100:1:1.2:120 for sulfide:Ti(OiPr)₄:ligand:H₂O₂ in CH₂Cl₂ at 0 °C for 3 h]. The reaction afforded good yield (84%) with a moderate enantioselectivity (62% ee) even with a lower catalyst loading from 1.0 to 0.5 mol%. The oxidations of methyl 4‐bromophenyl sulfide and methyl 4‐methoxyphenyl sulfide with H₂O₂ catalyzed by the Ti(OiPr)₄–L⁴ system gave 79–84% yields and 54–59% ee of the corresponding sulfoxides in CH₂Cl₂ at 20 °C. The chiral induction capability of the cumenyl‐modified sterically hindered Schiff bases for sulfoxidation was compared with the conventional Schiff bases bearing tert‐butyl groups at the 3,5‐positions of the salicylidenyl unit. Copyright © 2011 John Wiley & Sons, Ltd.     

Influence of substituents in the salicylaldehyde‐derived Schiff bases on vanadium‐catalyzed asymmetric oxidation of sulfides

A series of chiral Schiff bases ( L ¹ – L ⁵ ) with different substituents in the salicylidenyl unit were prepared from condensation of 3‐aryl‐5‐ tert ‐butylsalicylaldehyde derivatives and optically active amino alcohols. Bromination of 3‐phenyl‐5‐ tert ‐butylsalicylaldehyde gave an unexpected product 3‐(4‐bromophenyl)‐5‐bromosalicylaldehyde, from which the corresponding Schiff base ligands L ⁶ and L ⁷ , derived from (S)‐valinol and (S)‐ tert ‐leucinol, respectively, were prepared. Ligands L ¹ – L ⁷ were applied to the vanadium‐catalyzed asymmetric oxidation of aryl methyl sulfides. Under the optimal conditions, the oxidation of the thioanisole with H₂O₂ as oxidant in CH₂Cl₂ catalyzed by VO(acac)₂‐ L ¹ – L ⁷ gives good yields (74–83%) with moderate enantioselectivity (58–77% ee). Ligand L ⁷ , containing a 4‐bromophenyl group on the 3‐position and a Br atom on the 5‐position of the salicylidenyl moiety, displays an 80–90% ee for vanadium‐catalyzed oxidation of methyl 4‐bromophenyl sulfide and methyl 2‐naphthyl sulfide. Copyright © 2008 John Wiley & Sons, Ltd.     

新型酰基供体用于酶法动力学拆分制备(R)-1-(2-萘基)乙胺的研究

首次成功实现了光学纯(R)-1-(2-萘基)乙胺的高效酶法动力学拆分制备,考察了脂肪酶种类、溶剂、酰基供体、底物浓度、反应温度等对拆分效果的影响,发现新型酰基供体——正戊酸对氯苯酯能够很好地抑制非酶促自催化酰胺化效应.在甲苯溶剂中,底物浓度300 mmol/L,40℃条件下,采用该供体在脂肪酶Novozym 435催化下,动力学拆分反应8 h转化率达到理论最佳值50%,eep>99%.     

有机溶剂中(R)-醇腈酶催化不对称合成(R)-苯乙醇腈

 研究了来源于杏仁的（R）－醇腈酶在有机溶剂异丙醚中催化苯甲醛与HCN不对称合成（R）－苯乙醇腈，初步探讨了来源于不同杏仁的（R）－醇腈酶的筛选、最适酶量的确定以及底物HCN与苯甲醛的配比、底物浓度、酶的微环境pH和反应温度对不对称合成反应的影响．结果发现，来源于苦杏仁的（R）－醇腈酶优于来源于甜杏仁的（R）－醇腈酶．优化的反应条件为：最适酶量150g／L，HCN与苯甲醛的配比2．5，苯甲醛浓度300mmol／L，酶的微环境pH5．4，反应温度0～5℃．在该优化反应条件下，反应平衡转化率和产物的光学纯度均高达99％以上．     

(+)-(1S,2S,5R)-8-联苯薄荷醇的合成

以(R)-( )-pu legone为起始原料,经1,4-加成,还原两步反应合成了手性辅助试剂( )-(1S,2S,5R)-8-联苯薄荷醇及其差向异构体(-)-(1R,2S,5R)-8-联苯薄荷醇,总产率95%。其结构经1H NMR,13C NMR,IR,MS和X-射线衍射仪表征。     

手性噻唑烷-铑(I)配合物催化的苯乙酮不对称硅氢化反应

由L-半胱氨酸甲酯与α-吡啶甲醛缩合制备了2-(α-吡啶基)-4-羧甲基-1, 3-噻唑烷手性配体。用该手性配体与[Rh(COD)]2反应原位生成的Rh(I)配合物为催化剂进行了苯乙酮的不对称硅氢化反应。反应的化学产率达91%, 光学产率达82.1%e.e.。考察了各种反应条件对催化剂性能的影响。     

由(1R,2S)-麻黄碱制备的硼杂噁唑烷催化甲硼烷不对称还原苯乙酮

由(1R,2S)-麻黄碱制得了五个新的手性硼杂(口恶)唑烷1～5,它们催化甲硼烷不对称还原苯乙酮,获得了高产率的具有38.5～72.4％e.e.的R-1-苯基乙醇。讨论了催化剂的结构-活性关系及反应参数(催化剂用量、反应温度)对还原反应对映选择性的影响。     

First Asymmetric Total Synthesis of (R,E)-1-[4-(3-Hydroxyprop-1-enyl)phenoxyl]-3-methylbutane-2,3-diol

A new anti-inflammatory active phenylpropenoid, (R,E)-1-[4-(3-hydroxyprop-1-enyl) phenoxyl]-3-methylbutane-2,3-diol (1), isolated from the stem wood of Zanthoxylum integrifoliolum, has been synthesized for the first time using commercially available 4-hydroxy benzaldehyde (2). The key step involves the Sharpless asymmetric dihydroxylation of olefin (3).

(2S)-(+)-2-溴-1-(6'-甲氧基-2'-萘基)丙-1-酮的不对称合成

以(2R,3R)-酒石酸二甲酯为手性辅助剂,6-甲氧基-2-丙酰基萘经缩酮化、溴化铜不对称溴化、水解等反应合成了(2S)-2-溴-1-(6'-甲氧基-2'-萘基)丙-1-酮。总收率94%。     

Asymmetric Synthesis of (3R, 5R)-3-((tert-Butyldimethylsily)oxy)-5-((Z)-2-Bromovinyl)-Tetrahydro-Furan-2-one, an Intermediate for the Synthesis of Fostriecin

Fostriecin(CI-920) 11 a potential anticancer agent presently in phase I clinical trials at NCI is a novel phosphate ester produced by Streptomyces pulveraceus. Scheme 1 1 2 3 5 4 Synthesis of C10 epimer of compound 1 had been reported by Just G2. during the determination of its structure. On the basis of Just’s synthesis, a revised retro-asymmetric synthetic route of Fostriecin (scheme 1) was designed here of which compound 3 was synthesized from 5 with C3 in R configuration correspondi…     

Study on Bicoordination Chiral Inducement Catalysis of （R）-4-Thiazolidinecarboxylic Acid

The bicoordination chiral inducement catalysis of (R)-4-thiazolidinecarboxylic acid in the enantioselective borane reduction of prochiral ketones has been studied. The fact that the absolute configuration of the main product can be changed by simply using different operation methods was firstly verified. And the reason of bicoordination chiral inducement was discussed.     

用(R)-(+)-缩水甘油的亲核开环反应制备手性连二醇

以D-甘露醇为原料合成(R)-(+)-缩水甘油1。该环氧化合物的亲核开环反应为高立体选择性地(93%-96%e.e.)制备各种手性连二醇提供了一条简便途径。     

Preparation of (R)-2-chloro-1-(m-chlorophenyl)ethanol by Lipozyme TL IM-catalyzed second resolution

(R)-2-Chloro-l-(m-chlorophenyl)ethanol,a precursor of(R)-3-chlorostyrene oxide which is the key chiral intermediate for the preparation of severalβ3-adrenergic receptor agonists was prepared in 40%yield and 99%ee by the Lipozyme TL IM-catalyzed second resolution of the corresponding racemate in the presence of vinyl acetate.     

采用通透性处理的安大略假丝酵母全细胞高效合成(R)-2-氯-1-(3-氯苯基)乙醇(英文)

考察了利用安大略假丝酵母(Candida ontarioensis)静息细胞不对称催化2-氯-1-(3-氯苯基)乙酮合成(R)-2-氯-1-(3-氯苯基)乙醇的转化反应条件.结果表明,当底物浓度为10g/L时,在最适转化条件下反应72h,产物的ee值和产率分别达到99.9%和99.0%.采用4g/L十六烷基三甲基溴化铵对Candida ontarioensis细胞于4℃通透性处理20min后,全细胞的酶活提高2倍以上.当底物浓度提高为30g/L,转化24h后,产物的ee和产率分别达到99.9%和97.5%.该研究为高效制备(R)-2-氯-1-(3-氯苯基)乙醇提供了可行途径,并为生物催化合成芳基手性醇类手性中间体提供了理论指导。     

消旋的有机二磺酸三邻菲咯啉锌配合物(英)

Compound [Zn(phen)₃][BDA] (1) (BDA=6,6′-dibromo-2,2′-dimethoxy-1,1′-binaphthylene-4,4′-disulfonate, phen= 1,10-phenanthroline) composes of the anion part (racemic-(R,S)-6,6′-dibromo-2,2′-dimethoxy-1,1′-binaphthylene-4,4′-disulfonate ) and the cation part which consists of a racemic octahedrally coordinated zinc center defined six nitrogen atoms from three phen rings to form an inorganic chirality that can be resolution by chiral organic ligand, the 3D framework was formed through the strong H-bonding interaction between sulfonate and water. CCDC: 277924.     

(1R,2R)-(+)-(1,2)-DPEN-Bonded Sulfonic Acid Resin: A Trifunctional Heterogeneous Catalyst for Asymmetric Michael Additions of Acetone to Nitroolefins

Based on (1R,2R)-(+)-(1,2)-DPEN skeleton, a series of primary amine–sulfamide bifunctional catalysts were synthesized, which exhibited excellent catalytic performance in the Michael addition of acetone to β-nitrostyrene. Therefore, a trifunctional heterogeneous catalyst was designed and prepared by simple N-sulfonyl reaction of (1R,2R)-(+)-(1,2)-DPEN and sulfonyl chloride resin. It was employed for the aforementioned addition without any additive and satisfactory results (80.5% conversion; 84.3% ee) were obtained. Meanwhile, the structural and textural properties of the catalyst were characterized by infrared spectroscopy (FT-IR), elemental analysis, SEM, and N₂ adsorption and desorption experiments. Finally, the generality of the catalyst was investigated.