Solid Phase Synthesis of 4H-Pyrimido[2,1-b] Benzothiazol-4-ones from Resin-Bound Cyclic Malonic Ester

The solid phase synthesis of 4H-pyrimido[2,1-6] benzothizaol-4-ones has been reported.     

The absence of nitrone form in re-determined crystal structure of 2-hydroxyimino-3-methyl-4-nitro-2,5-dihydrothiophene 1,1-dioxide

Crystal and molecular structures of 2-hydroxyimino-3-methyl-4-nitro-2,5-dihydrothiophene-1,1-dioxide C₅H₆N₂O₅S (I) have been re-determined by single crystal X-ray diffraction analysis. The structure of I (space group P2₁2₁2₁, a = 6.124(1) Å, b = 9.205(2) Å, c = 14.884(3) Å, Z = 4) was solved by the direct method and refined anisotropically in the full-matrix approximation to R = 0.064 using all 1756 measured independent reflections (automated diffractometer CAD-4, λCuK_α, anomalous scattering taken into account). This study proves that the compound I contains a disordered group H-O-N=C, but not the isomeric nitrone group O←N(H)=C, as it has been concluded by the workers who pioneered single crystal X-ray diffraction study of I and erroneously took the second low-occupied oxygen position of the disordered hydroxyimine group for H at N atom.     

2',3'-二脱氧-2',3'-二去氢鸟嘌呤核苷构象稳定性的理论研究

采用密度泛函方法在B3LYP/6-31＋G**水平上研究了2',3'-二脱氧-2',3'-二去氢鸟嘌呤核苷分子(D4G)的构象. 分别研究在气相中的孤立分子和一水合物异构体的相对稳定性和异构体之间的相互转变过程, 分析了水分子的参与对D4G异构体的相对稳定性和几何结构参数以及自然电荷的影响. 结果表明, 孤立的D4G分子在气相中存在8种稳定构象, 其中构象d4g-2是所有构象中最稳定的, 气相中D4G主要以d4g-2存在. 气相中各构象的相对稳定性为: d4g-2＞d4g-1＞d4g-5＞d4g-3＞d4g-6＞d4g-4＞d4g-8＞d4g-7. 计算得到的各构象键长和键角数据与实验值接近. 一个水分子的加入对D4G分子的构型参数有所影响, 基本不改变D4G分子各构象的稳定性顺序, 但构象转变的能垒有所提高. 氢键在分子构象中发挥了重要作用.     

Thermodynamic study of the three isomers of bromo and iodobenzoic acids. Part II

Using our technique of combustion of small amount of a substance, we determined by calorimetry the standard molar enthalpy of formation in the condensed state and atT=298.15 K of the three isomers of bromo and iodobenzoic acids. Associating to these values their standard molar enthalpies of sublimation previously measured, it was possible to determine their standard molar enthalpies of formation in the gaseous state and atT=298.15 K. The experimental values of the thermodynamic properties _f H _m ^o (cr, 298.15 K), _f H _m ^o (cr, 298.15 K), _sub H _m ^o (298.15 K), and _f H _m ^o (g, 298.15 K) are given for the two series. From the experimental value of the standard molar enthalpy of atomization, it was possible to determine an enthalpy value for the C_b-Br and C_b-I bonds. The experimental and theoretical values of the resonance energy of bromo and iodobenzoic acids are compatible. The relative stability of some monosubstituted derivatives of benzoic acid studied in our laboratory is also discussed.Part I is concerned with Ref. 22 (for bromobenzoic acids) and with Ref. 23 (for iodobenzoic acids).     

Solution and X-Ray Crystal Structures of the Di- and Tetra-allyl Ether of tert- utylcalix[4]arene

The di- and tetra-allyl ethers of tert-butylcalix[4]arene 1 and 2 have been prepared by alkylation of tert-butylcalix[4]arene with allyl bromide and K₂CO₃ using different reaction times. Solution ¹H NMR measurement of the di-allyl ether 1 and X-ray crystal structures of the complexes of 1 with chloroform (1a) or methanol (1b) indicate the cone conformation of 1 in which intramolecular hydrogen bonding can be maximized. The crystalline state conformers 1a and 1b are distorted in different grades depending on the solvent. While methanol is incorporated in the macrocycle, chloroform molecules do not occupy the cage. The solution ¹H NMR spectra of tetra-allyl ether 2 show the co-existence of the cone and partial cone conformation. The partial cone conformer of 2 was investigated by X-ray crystallography. In this compound hydrogen bonding is not existent. The conformer distribution is likely affected by steric and template effects.     

Non-catalytic Addition of 1,2,4-Triazole to Nucleophilic and Electrophilic Alkenes

Non-catalytic addition of 1,2,4-triazole to vinyl ethers and esters occurs on heating (65-175°C, 4-20 h) to give Markovnikov adducts (yield 30-100%). Electron-deficient alkenes (acrylonitrile, acrylic acid, 4-phenyl-3-buten-2-one) react with 1,2,4-triazole (78-190°C, 4-20 h) to give anti-Markovnikov adducts in yields of 45-83%.     

Cu/SO42-/La2O3-ZrO2-Al2O3催化剂的制备及其对C3H6选择还原NO的催化性能

以Al₂O₃为基质，添加ZrO₂和La₂O₃，制成La₂O₃-ZrO₂-Al₂O₃复合载体，然后采用SO₄^2-进行改性，再负载上Cu²⁺，制备了铜基SO₄^2-改性的复合载体催化剂(Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃)。考察了它在富氧条件下对丙烯选择还原NO的催化性能，并借助XRD、SEM、TG、Py-IR、NH₃-TPD、FTIR和TPR等方法研究了Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃的结构和性能的关系。结果表明，ZrO₂的加入主要有利于提高催化剂的低温活性；La₂O₃的加入则主要有利于提高催化剂的热稳定性和还原性能；SO₄^2-能够与Zr形成螯合双配位结构，大幅度促使催化剂表面酸量增加并且酸性增强；因此，有效地提高了Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃在富氧条件下对丙烯选择还原NO的催化活性和水热稳定性。在无水条件下，Cu/SO₄^2-/La₂O₃-ZrO₂-Al₂O₃能使NO的最大转化率高达84.3%，即使在275 ℃ 10%水蒸气存在的情况下，仍能使NO的转化率高达81.2%。     

A new approach to the facile synthesis of mono- and disubstituted quinazolin-4(3H)-ones under solvent-free conditions

Quinazolin-4(3H)-one derivatives were synthesized successfully via a one-pot, three component reaction of isatoic anhydride and an orthoester with ammonium acetate or a primary amine catalyzed by silica sulfuric acid under solvent-free conditions. This is the first report on the synthesis of 2-substituted quinazolin-4(3H)-ones by this procedure.