Enzymatic kinetic resolution of racemic 4-tetrahydropyranols by Candida rugosa lipase

Enzymatic kinetic resolution of (±)-hydroxytetrahydropyrans has been achieved for the first time by means of lipase-mediated transesterification to afford optically active (2S,4R)-tetrahydropyranyl acetates and (2R,4S)-tetrahydropyranols in excellent yields with high enantioselectivity. Absolute configurations of the tetrahydropyranyl acetates were assigned as (S) by chemical correlation.     

Efficient dynamic kinetic resolution of secondary amines with Pd on alkaline earth salts and a lipase

Combination of Pd, supported on alkaline earth type supports with a lipase results in a selective catalytic system for dynamic kinetic resolution of benzylic amines.     

Aldehyde-based racemization in the dynamic kinetic resolution of N-heterocyclic α-amino esters using Candida antarctica lipase A

The present research introduces approaches for the dynamic kinetic resolution of the methyl esters of proline and pipecolic acid. As the result, a method was developed which is based on the acylation of the secondary amino group of the amino esters with vinyl butanoate by Candida antarctica lipase A. In the optimized method, acetaldehyde as a racemizing agent is released in situ from vinyl butanoate in the presence of triethylamine, allowing ca. 90% of the racemic proline and 70% of the pipecolic acid methyl esters to be acylated in the forms of highly enantiopure (ee=97%) butanamides with the S-absolute configurations.     

一种SO2固定及用于制备BaSO3或BaSO4的方法

在常温常压下,由乙二胺（EDA）和乙二醇及其衍生物（EGs）组成的混合体系可捕集SO₂并转化为一种SO₂储集材料（SO₂SM）。EDA+EGs体系呈现了强的捕集性能（0.364~0.662 g_SO2·g_absorbent^-1）。FTIR,XPS和XRD结果确证了SO₂SM为一种烷基亚硫酸盐。以EG-SO₂SM为原料制备具有多种形貌的BaSO₃或BaSO₄,在此过程中,EG-SO₂SM不仅提供了原材料,而且可以释放EDA和EG用作表面活性剂,调控晶体的结晶化过程。     

一种SO2固定及用于制备BaSO3或BaSO4的方法

在常温常压下,由乙二胺（EDA）和乙二醇及其衍生物（EGs）组成的混合体系可捕集SO₂并转化为一种SO₂储集材料（SO₂SM）。EDA+EGs体系呈现了强的捕集性能（0.364~0.662 g_SO2·gabsorbent^-1）。FTIR,XPS和XRD结果确证了SO₂SM为一种烷基亚硫酸盐。以EG-SO₂SM为原料制备具有多种形貌的BaSO₃或BaSO₄,在此过程中,EG-SO₂SM不仅提供了原材料,而且可以释放EDA和EG用作表面活性剂,调控晶体的结晶化过程。     

A convenient synthesis of fluoroalkylated γ-butyrolactones from polyfluoroalkyl iodides and 4-pentenoic acid catalyzed by Pd(PPh3)4

A convenient synthesis of fluoroalkylated γ-butyrolactones was realized through the reaction of fluoroalkyl iodides with 4-pentenoic acid in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium and sequential treatment with triethylamine in 79-85% yields.     

Synthesis of (R)-propane-1,2-diol from lactides by dynamic kinetic resolution

The dynamic kinetic resolution (DKR) of rac-1-tert-butoxypropan-2-ol with isopropenyl acetate in the presence of Novozyme 435 and a ruthenium catalyst produces enantiomerically pure (R)-1-tert-butoxy-2-acetoxy-propane (>99.5 %ee) in a good yield. The product can be easily transformed into (R)-propane-1,2-diol without loss of stereoselectivity. Together with recently published procedures, the herein described DKR offers the possibility to use any lactide source as starting material for the production of (R)-propane-1,2-diol. The chiral diol may serve as the chiral building block for the synthesis of important enantiopure esters, like propylene carbonate, chiral polymers, etc.     

Asymmetric synthesis of (S)-vigabatrin and (S)-dihydrokavain via cobalt catalyzed hydrolytic kinetic resolution of epoxides

A concise route to the asymmetric synthesis of (S)-vigabatrin^® and (S)-dihydrokavain has been described using Co-catalyzed hydrolytic kinetic resolution of racemic epoxides and regiospecific opening of terminal epoxides with dimethylsulfonium methylide as the key steps.     

Asymmetric ring opening of terminal epoxides via kinetic resolution catalyzed by chiral (salen)Co mixture

The highly enantioselective hydrolytic kinetic resolution (HKR) of racemic terminal epoxides by bimetallic chiral (salen)Co and (salen)Co(III)-OAc mixture provides a simple and effective method for the synthesis of enantiomerically enriched terminal epoxides (ee > 99%) and diols. At the equimolar amounts of bimetallic chiral (salen)Co and (salen)Co(II)-OAc, the catalytic activity increases more than two times in comparison with (salen)Co(III)-OAc used alone. The mixed catalytic system can be recycled and reused. No significant loss of catalytic activity was observed after three runs.     

Candida antarctica lipase B-catalyzed synthesis of acetamides using [BMIm(PF6)] as a reaction medium

An efficient protocol has been developed for synthesis of acetamides using Candida antarctica lipase B (CaL B) in [BMIm(PF₆)] as a greener reaction medium. The reaction is applicable to a wide variety of aliphatic esters/acetic acid and amines providing excellent yields of corresponding acetamide. The catalyst exhibits remarkable activity and is reusable for up to four consecutive cycles.     

Hexene-1 isomerization catalyzed by the Pd(acac)2?BF3OEt2 system

The data of IR and UV spectroscopic studies of the interaction of Pd(acac)₂+BF₃OEt₂ in the presence of hexene-1 suggest the formation of a Pd–C bond through³C of the acetylacetonate ligand. In the first step of isomerization hexene-1 converts largely (94.5%) to hexene-2.

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- Pd(acac)₂+BF₃OEt₂ -1 , Pd–C ³C- ; , -1 -2, , 94,5%.

     

Fast racemization and dynamic kinetic resolution of primary benzyl amines

We prepared a Pd nanocatalyst (average diameter of Pd nanoparticles = 1.73 nm) displaying a remarkable activity for the racemization and dynamic kinetic resolution (DKR) of 1-methylbenzylamine. It was eight times more active than the previous best. The DKR of 1-methylbenzylamine with the Pd nanocatalyst (2 mol %) in the presence of a thermostable lipase (Novozym 435) was complete in 6 h at 70 °C. The DKRs of other benzyl amines also proceeded to completion in 6 h under similar conditions except the amount of Pd nanocatalyst.     

Dehydrocoupling reactions of amines with silanes catalyzed by [(Et2N)3U][BPh4]

Dehydrocoupling reactions of primary amines RNH₂ with PhSiH₃ were catalyzed by [(Et₂N)₃U][BPh₄] to give the corresponding aminosilanes PhSiH_3−n(NHR)_n (n=1–3), the relative yields of the products were found to be dependent on the experimental conditions and on the nature of R. For a primary silane (PhSiH₃), the reactivity of RNH₂ follows the order primary>secondary>tertiary. Similar dehydrocoupling reactions using secondary amines with secondary silanes were found to be less reactive. Homodehydrocoupling of the silane was found not to be a competing reaction at room temperature. The hydride [(RNH)₂UH][BPh₄], which is plausibly formed in the reaction of [(RNH)₃U][BPh₄] with PhSiH₃ is a likely intermediate in the catalytic cycle.     

New open-framework in the uranyl vanadates A3(UO2)7(VO4)5O (A=Li, Ag) with intergrowth structure between A(UO2)4(VO4)3 and A2(UO2)3(VO4)2O

New uranyl vanadates A₃(UO₂)₇(VO₄)₅O (M=Li (1), Na (2), Ag (3)) have been synthesized by solid-state reaction and their structures determined from single-crystal X-ray diffraction data for 1 and 3. The tetragonal structure results of an alternation of two types of sheets denoted S for _∞²[UO₂(VO₄)₂]⁴⁻ and D for _∞²[(UO₂)₂(VO₄)₃]⁵⁻ built from UO₆ square bipyramids and connected through VO₄ tetrahedra to _∞¹[U(3)O₅-U(4)O₅]⁸⁻ infinite chains of edge-shared U(3)O₇ and U(4)O₇ pentagonal bipyramids alternatively parallel to a- and b-axis to construct a three-dimensional uranyl vanadate arrangement. It is noticeable that similar _∞[UO₅]⁴⁻ chains are connected only by S-type sheets in A₂(UO₂)₃(VO₄)₂O and by D-type sheets in A(UO₂)₄(VO₄)₃, thus A₃(UO₂)₇(VO₄)₅O appears as an intergrowth structure between the two previously reported series. The mobility of the monovalent ion in the mutually perpendicular channels created in the three-dimensional arrangement is correlated to the occupation rate of the sites and by the geometry of the different sites occupied by either Na, Ag or Li. Crystallographic data: 293 K, Bruker X8-APEX2 X-ray diffractometer equipped with a 4 K CCD detector, MoKα, λ=0.71073 Å, tetragonal symmetry, space group P4¯m2, Z=1, full-matrix least-squares refinement on the basis of F²; 1,a=7.2794(9) Å, c=14.514(4) Å, R1=0.021 and wR2=0.048 for 62 parameters with 782 independent reflections with I?2σ(I); 3, a=7.2373(3) Å, c=14.7973(15) Å, R1=0.041 and wR2=0.085 for 60 parameters with 1066 independent reflections with I?2σ(I).     

PbMn(SO4)2: A new chiral antiferromagnet

PbMn(SO₄)₂ has been synthesized in an evacuated quartz tube. The nuclear and magnetic crystal structures have been determined using powder X-ray and neutron diffraction. This material crystallizes in the enantiomorphic space group pair P4₁2₁2(92) and P4₃2₁2(96), forming a double-helical arrangement of Pb²⁺ and Mn²⁺ cations. The Mn²⁺O₆ octahedra are distorted. Each 3d⁵ Mn²⁺ has four nearest-neighbors and four next-nearest-neighbors adopting a frustrating arrangement. The compound orders antiferromagnetically at 5.5 K. Field dependent specific heat and magnetization measurements show that T_N is suppressed to 3.3 K when μ₀H=9 T.     

Structures Of Tetraammine Salts [Pt(NH3)4](N03)2, [Pd(NH3)4](N03)2, and [Pd(NH3)4]F2 H20

This contribution presents the results of a single crystal X-ray diffraction study of three ammine complexes of bivalent platinum and palladium: [Pt(NH₃)₄](N0₃)2, [Pd(NH₃)₄](N0₃)₂ and [Pd(NH₃)₄]F₂H₂O. The first two compounds are isostructural; metal atoms are located on inversion centers, all other atoms are in general positions. A three-dimensional framework is built from planar-square complex cations and nitrate ions joined by N-H...O hydrogen bonds. In [Pd(NH₃)₄]F₂H₂O, palladium atoms, as in the previous cases, are located on inversion centers, while oxygen atoms of water molecules are on the two-fold symmetry axis. A network of strong N-H...F and O-H...F hydrogen bonds linking the cations, anions, and crystallization water molecules is present in the structure.     

Kinetics of homogeneous acetoxylation of cyclododecene and 1,5,9-cyclododecatriene catalyzed by Pd(OAc)2

The kinetics of acetoxylation of cyclododecene and (E,E,E)-1,5,9-cyclododecatriene catalyzed by Pd(OAc)₂ has been studied in glacial acetic acid solutions at 323–343 K and atmospheric pressure. The experimental data were described by kinetic equations of the Michaelis-Menten type.     

An efficient Stille cross-coupling reaction catalyzed by Pd(OAc)2/DAB-Cy catalytic system

An efficient palladium-catalyzed Stille cross-coupling reaction has been developed. In the presence of 3 mol% of Pd(dba)₂ and 6 mol% of DAB-Cy (1,4-dicyclohexyl-diazabutadiene), various aryl halides (iodides and bromides) were coupled with organotin compounds to afford the corresponding biaryls and alkyne in good to excellent yields. Furthermore, high TONs [turnover numbers, TONs up to 950,000 for the reaction of 1-iodo-4-nitrobenzene and tributyl(phenyl)stannane] for the Stille cross-coupling reaction were observed.     

Structures, energy bands and conductivities of (Me3NEt)[Pd(dmit) 2]2 and (NEt4)[Pd(dmit) 2]2

The electrical conductive molecular crystals (Me₃NEt)[Pd(dmit) ₂]₂ and (NEt₄)[Pd (dmit) ₂]₂ (dmit = 4,5-dimercapto-1,3-dithiole-2-thione) have been prepared, and their crystal structures and conductivity-temperature curves have been determined. The fact that the conductivity at room temperature of (Me₃NEt)[Pd(dmit) ₂]₂ (σ = 58 Ω^-1 cm^-1) is much higher than that of (Net₄)-[Pd(dmit)₂]₂ (σ = 2.2 Ω^-1.cm^-1) has been rationally explained by the results of energy band calculations. (MeNEt₃)[Pd(dmit)₂]₂ belongs to monoclinic system, P2₁/m space group and (Net₄)[Pd (dmit)₂]₂ belongs to triclinic system, space group. The structural conducting component of the crystals is the planar coordinative anion [Pd(dmit)₂]^0.5- which forms the face-to-face dimmer. [Pd(dmit)₂]^- ₂These dimers have been further constructed to be a kind of two-dimensional (2-D) conductive molecular sheet by means of S_S intermolecular interactions. The tiny difference of the above 2-D molecular sheets of the two title crystals has resulted in one order of magnitude difference of conductivities.