Enantioselective Synthesis of Tertiary α-Hydroxy Phosphonates Catalyzed by Carbohydrate/Cinchona Alkaloid Thiourea Organocatalysts

A pinch of sugar: The new bifunctional carbohydrate/cinchonine-based thiourea 1 has been designed for the asymmetric addition reaction of α-ketophosphonates and trimethylsilyl cyanide, the product of which can be hydrolyzed to afford tertiary α-hydroxy phosphonates with excellent enantioselectivities.     

STRUCTURES OF COPPER(I) AND ZINC(II) COMPLEXES WITH N,N′-BIS(2-PYRIDINYL)THIOUREA (BPT)

Abstract

Copper(I) and zinc(II) complexes with N,N′-bis(2-pyridinyl)thiourea (BPT), [Cu(BPT)₂]ClO₄ (1) and [Zn(BPT)₂](ClO₄)₂ (2) were synthesized by reaction of M(ClO₄)₂ (M = Cu, Zn) with BPT in methanol solution. The crystal structures of complexes (1) and (2) were characterized by X-ray diffraction: (1) is triclinic, space group P, with a = 10.162(2), b=14.483(6), c = 9.496(2) Å, α = 105.80(2)°, β = 106.94(2)°, γ = 82.71(3)°, V = 1284.4(7) ų, Z = 2, and final R = 0.047, R _w = 0.061; (2) is monoclinic, space group C2/c, with a = 15.15(1), b = 6.299(3), c = 30.16(1)Å, β = 93.49(7)°, V = 2872(2)ų, Z=4, and final R = 0.049, R_w = 0.070. Both of the complexes exhibit novel structures. Two N atoms and two S atoms from two BPT groups coordinate to one M atom. The M atom shows distorted tetrahedral geometry. IR spectra and ther-moanalyses of BPT and its complexes (1) and (2) are briefly discussed.     

A Rapid Process for Producing Cellulose Multi‐Filament Fibers from a NaOH/Thiourea Solvent System

Summary: Cellulose was dissolved rapidly in 9.5 wt.‐% NaOH and 4.5 wt.‐% thiourea aqueous solution pre‐cooled to −5 °C to prepare a transparent solution. Novel cellulose multi‐filament fibers were spun successfully, for the first time, from the cellulose dope on an extended laboratory scale. The results from ¹³C NMR, scanning electron microscopy and wide angle X‐ray diffraction (WAXD) patterns indicated that the fibers exhibited cellulose II character and possessed a circular cross‐section and smooth surface. The tensile strength of the novel fibers reached 1.9–2.2 cN · dtex⁻¹. 2D WAXD and SAXS patterns revealed that, with a drawing progress, the orientation factor increased and mechanical properties were improved.

SEM micrographs of the novel multi‐filament fibers spun from cellulose solution in a NaOH/thiourea aqueous system pre‐cooled to −5 °C on an extended laboratory scale.     

Temporal electronic structures of nonresonant Raman excited virtual states: a case study of ethylene thiourea

An algorithm is employed to elucidate molecular bond polarizabilities of ethylene thiourea including their temporal relaxation from Raman intensities, which provide much information concerning the electronic distribution of nonresonant Raman excited virtual states. The main character of the excited states of ethylene thiourea is that the excited electrons tend to flow to the molecular periphery because of electronic repulsion. It is noted that the bond electronic densities of the ground state can be mapped out by the bond polarizabilities at the final stage of relaxation. The relaxation time is shown to be proportional to the wavelength of the exciting light in agreement with Heisenberg's uncertainty principle, showing that the excitations are indeed not the stationary eigenstates. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and Structure of N-Ethoxycarbonyl-N′-O-Methoxyphenylthiourea

N-ethoxycarbonyl-N′-o-methoxyphenylthiourea was synthesized and characterized by elemental analysis, TG-DTA analysis, IR, and ¹H NMR spectrum, and single crystal X-ray diffraction analysis. The compound crystallizes as a planar molecule in the monoclinic space group P2(1)/c, with a = 9.690(2)Å, b = 8.595(2)Å, c = 15.944(4)Å, α = 90°, β = 106.467(4)°, γ = 90°, and D_calc = 1.326 g/cm³ for Z = 4. Intramolecular H-bonds promote the stability of the title compound and change the coordination ability of the thiourea ligand. Intermolecular N─H…S H-bonds link pairs of two molecules.     

Eco-friendly polyethylene glycol-400: a rapid and efficient recyclable reaction medium for the synthesis of thiazole derivatives

Abstract

An efficient and convenient procedure for the synthesis of thiazole derivatives from α-haloketone, thiourea and substituted acetophenones using polyethylene glycol-400 as a green and recyclable solvent is described. Significant rate enhancement and improved yields have been observed.     

A New Simple Voltammetric Method for Thiourea and Thiourea Dioxide Determinations

Abstract

Linear sweep voltammetry at glassy carbon or other carbon materials is shown to be a simple, highly sensitive, and relatively versatile analytical method for the determination of thiourea and thiourea dioxide. Using the first one-electron oxidation peak occurring at ～0.6V, thiourea can be determined directly in a variety of electrolytes from concentrated acids to solutions of pH ～5. The thiourea dioxide determination is based on the two-electron oxidation peak which appears in a number of electrolytes at ～1.2V.     

(NH_2)_2CSO_2与Co~(2 )-NH_3体系定向反应的研究

研究了温度、酸碱度、Hg( )等因素对 ( NH2 ) 2 CSO2 与 Co2 - NH3体系定向反应的影响 ,发现该体系同时存在单电子反应和双电子反应 ,并相互竞争 ,( NH2 ) 2 CSO2 的双电子反应率随着体系温度、p H值增大和 Hg( )离子的加入而增高 .探讨了反应机理 ,并对两种反应的变化方向作了机理解释 .     

硫脲在铂电极表面吸附行为的表面增强拉曼光谱研究

本文通过电化学方法有效抑制了硫脲在铂电极表面的解离,从而实现了用SERS技术研究粗糙铂电极表面硫脲的吸附行为。结果表明,硫脲分子是以硫端斜躺吸附在电极表面,随着电位变负渐渐转为直立。     

N'-(4,6-二取代嘧啶-2-基)氧化烟酰硫脲的合成与生物活性测定

合成并表征了9种未见文献报道的N'-(4,6-二取代嘧啶-2-基)氧化烟酰硫脲衍生物3, 结构经IR, ¹H NMR, 元素分析得到确证. 初步的生物活性测试表明化合物3a具有较好的除草活性, 化合物3b具有一定的杀虫活性.