四氢噻吩合成方法的改进

以1,4-二氯丁烷和硫化钠为原料,碘为催化剂,乙醇为溶剂合成了四氢噻吩。最佳反应条件:1,4-二氯丁烷50 mmol,n(1,4-二氯丁烷)∶n(硫化钠)=1.0∶1.3,碘10 mg,回流反应3 h时,产率91.79%,纯度≥99%(GC)。     

2-噻吩乙酸的合成

以噻吩为原料,经乙酰基反应、氧化重排生成2-噻吩乙酸甲酯(2),2经水解得2-噻吩乙酸(3),总收率53．0％,其结构经IR和^1H NMR确证。     

3-氨基-二氢噻吩-2-酮类Schiff碱的合成和生物活性研究

通过3-氨基-二氢噻吩-2-酮(DL-高半胱氨酸硫内酯)盐酸盐与取代苯甲醛反应, 得到3-氨基-二氢噻吩-2-酮类Schiff碱. 合成了9个化合物, 其中7个为首次报道的新Schiff碱类化合物. 化合物结构经IR, ¹H NMR和元素分析证实, 并对这些化合物进行了室内毒力测试, 结果表明此类化合物具有很好的杀菌、抑菌活性.     

3-氧代-4-甲酸甲酯四氢噻吩的合成工艺优化

以甲醇与巯基乙酸为起始原料合成了3-氧代-4-甲酸甲酯四氢噻吩(Ⅲ),产物通过₁H NMR,₁₃C NMR,HRMS等表征。研究了无机碱(NaHCO₃、Na₂CO₃、K₂CO₃、NaOH、KOH)与有机碱(乙胺、三乙胺、吡啶、甲醇钾),不同溶剂,以及温度对合成3-氧代-4-甲酸甲酯四氢噻吩收率的影响,结果表明：有机碱效果优于无机碱;甲苯为较优溶剂;温高反应有利于Ⅲ的合成。用甲苯作溶剂,吡啶为碱催化剂,在80℃下反应2小时,3-氧代-4-甲酸甲酯四氢噻吩收率达78%。     

含四氢噻吩类生物素杂质的合成

d-生物素(d-Biotin)又称维生素H、辅酶R,其已广泛应用于医药、家禽、家畜的营养和饲料添加剂方面[1-4].目前比较权威的质量标准是欧洲药典[5],其在美国药典[6]的基础上提出了5个有关物质(杂质A,B,C,D,E)的TLC控制.     

2-甲基噻吩光异构化成3-甲基噻吩的理论研究

用CASSCF方法以6-31G基组研究了2-甲基噻吩光异构化为3-甲基噻吩的光化学反应和基态(S₀)及三重激发态(T₁)的相关势能面.反应主要发生在三重态(T₁)上,其间经历了两个双自由基,1个三元环中间体及4个过渡态.沿着反应路径找到了2个T₁/S₀势能面交叉点,其结构都类似于双自由基.在第二个T₁/S₀势能面交叉点附近由T₁向S₀的系间窜越(ISC)最为有利.     

2-苯基噻吩的电化学聚合

聚噻吩及其衍生物是一类重要的导电高分子材料,它们具有良好的导电性、高度稳定性以及易于调控的分子链结构．因此,自从人们发现聚噻吩以来,噻吩类化合物,尤其是3-取代噻吩的聚合和表征一直受到人们的广泛关注[1,2]．相对而言,关于2-取代噻吩的聚合几乎还是空白,以往人们对其进行电化学聚合的尝试是不成功的[3]．     

甲苯、2-甲基噻吩和3-甲基噻吩的化学分离方法研究

报道了一种分离甲苯、2-甲基噻吩和3-甲基噻吩的方法。通过氯化反应将沸点非常接近的甲苯、2-甲基噻吩和3-甲基噻吩转化为沸点相差较大的甲苯(111℃)、2-氯-5-甲基噻吩(155℃)和2,5-二氯-3-甲基噻吩(185℃),通过对比实验获得氯代反应的最佳条件为:2-甲基噻吩和3-甲基噻吩与磺酰氯的投料比1∶1. 75,反应温度65℃,反应时间2 h。通过精馏将三者分离并提纯,得到甲苯、高附加值的2-氯-5-甲基噻吩和2,5-二氯-3-甲基噻吩产品;通过催化还原反应将2-氯-5-甲基噻吩和2,5-二氯-3-甲基噻吩分别还原为2-甲基噻吩和3-甲基噻吩,达到完全分离、提纯的目的。     

~(13)C-NMR研究3,4-聚异戊二烯的序列分布

Fe(acac)_3-Phen-AlEt_3 催化体系可使异戊二烯聚合成以 3,4-链节为主具有一定结晶性能的聚异戊二烯。本文对该聚合物的~(13)C-NMR 谱进行了全分析,研究了序列分布、微观结构。结果表明不同方法求得的微观结构含量很好地一致,说明对~(13)C-NMR 谱峰归属的正确性。并指出顺-1,4/3,4-序列中存在着头-头,尾-尾的连接方式,3,4-嵌段链节不足够长及存在反节可能是结晶度不太高的主要原因。     

聚噻吩取代效应的理论研究

用自洽场晶体轨道法（ＳＣＦ ＣＮＤＯ／２－ＣＯ）对聚噻吩的一些一取代物和二取代物的电子结构进行了研究，计算的取代基包括－ＣＨ３，－Ｃ２Ｈ５，－ＯＣＨ３和－ＣＮ。计算结果表明，这些取代基基本没有影响聚噻吩主链的平面结构，除聚－３，４－二甲基噻吩的主链发生了４０°的扭转外，其它衍生物的主链仍处于同一平面。根据各取代高分子的电子特性我们得到结论：给电子基团和吸电子基团的取代教师将使能隙（Ｅｇ）减小，价带     

1H and 13C-NMR data of hydroxyflavone derivatives

Many hydroxyflavone derivatives have been found in nature and shown to have many biological functions. Because their function is changed by the position and number of hydroxyl group, their structural identification is a fundamental and necessary step for understanding their functions. In the present study, the complete 1H and 13C NMR spectral assignments were presented for 6 hydroxyflavones, and NMR data of additional 14 hydroxyflavone derivatives were compared with those of the 6 hydroxyflavones. In addition, the partially incorrect NMR data of two of the dihydroxyflavones whose NMR data were previously reported were corrected.     

Theoretical Study of 13C Chemical Shifts Structures of Some ortho-Substituted 3-Anilino-2-nitrobenzo[b]thiophenes and 2-Anilino-3-nitrobenzo[b]thiophenes and Comparison with Experimental

¹³C NMR chemical shifts have been calculated for structures of some substituted 3‐anilino‐2‐nitrobenzo‐[b]thiophenes ( 2 o) and 2‐anilino‐3‐nitrobenzo[b]thiophenes ( 3 o) derivatives containing OH, NH₂, OMe, Me, Et, H, F, Cl and Br. The molecular structures were fully optimized using B3LYP/6‐31G(d,p). The calculation of the ¹³C shielding tensors employed the GAUSSIAN 03 implementation of the gauge‐including atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) by using 6‐311++G(d,p) basis set at density functional levels of theories (DFT). The isotropic and the anisotropy parameters of chemical shielding for all compounds are calculated. The predicted ¹³C chemical shifts are derived from equation δ=δ₀+δ where δ is the chemical shift, δ is the absolute shielding, and δ₀ is the absolute shielding of the standard TMS. Excellent linear relationships have been observed between experimental and calculated ¹³C NMR chemical shifts for all derivatives     

A 1H, 13C and 15N NMR study in solution and in the solid state of six N-substituted pyrazoles and indazoles

Three N-substituted pyrazoles and three N-substituted indazoles [1-(4-nitrophenyl)-3,5-dimethylpyrazole (1), 1-(2,4-dinitrophenyl)-3,5-dimethylpyrazole (2), 1-tosyl-pyrazole (3), 1-p-chlorobenzoylindazole (4), 1-tosylinda-zole (5) and 2-(2-hydroxy-2-phenylethyl)-indazole (6)] have been studied by NMR spectroscopy in solution (1H, 13C, 15N) and in the solid state (13C, 15N). The chemical shifts have been compared with GIAO/DFT calculated absolute shieldings. Some discrepancies have been analyzed.     

2,4,6-三甲氧基苯-1-O-D葡萄糖苷的核磁共振谱的理论研究

The 1H and 13C-NMR of 2,4,6-trimethoxyphenol-1-O-D-glucopyranoside(Compound 1) isolated from Celastrus angulatus (Celastraceae) was calculated theoretically at the both levels HF/6-311+G(2d,p)//B3LYP/6-31G(d) and HF/6-311+G(2d,p)//B3LYP/6-31G(d,p) using the GIAO (gauge-independent atomic orbital) method. Statistical error analysis for theoretically predicted δH and δC values versus those experimentally observed for compound 1 was discussed. The results show that the theoretically predicted δH and δC values of β conformer of compound 1 are more close to the experimentally observed values than α conformer, and the β conformer of compound 1 is more stable than α conformer according to molecular energy theoretically calculated. So compound 1 is assigned to be 2,4,6-trimethoxyphenol-1-O-β-D-glucopyranoside, which is in good consistence with the conclusion deduced by the anomeric proton signal (δH=4.80, J=7.3 Hz) experimentally observed.     

Remarks on GIAO-DFT predictions of 13C chemical shifts

Predicting (13)C chemical shifts by GIAO-DFT calculations appears to be more accurate than frequently expected provided that: (a) the comparison between experimental and theoretical data is performed using the linear regression method, (b) a sufficiently high level of theory [e.g. B3LYP/6-311 + + G(2d,p)//B3LYP/6-311 + + G(2d,p) or PBE1PBE/6-311 + G(2df,p)//B3LYP/6-311 + + G(2d,p)] is used, (c) the experimental data originate from the measurements performed in one solvent whose influence is taken into account at the molecular geometry optimization step and, first of all, during the shielding calculation, (d) the experimental data are free of heavy atom effects or such effects are appropriately treated in calculations, and finally (e) the conformational compositions of the investigated objects are known.     

DFT‐GIAO 1H and 13C NMR prediction of chemical shifts for the configurational assignment of 6β‐hydroxyhyoscyamine diastereoisomers

¹H and ¹³C NMR chemical shift calculations using the density functional theory–gauge including/invariant atomic orbitals (DFT–GIAO) approximation at the B3LYP/6‐311G++(d,p) level of theory have been used to assign both natural diastereoisomers of 6β‐hydroxyhyoscyamine. The theoretical chemical shifts of the ¹H and ¹³C atoms in both isomers were calculated using a previously determined conformational distribution, and the theoretical and experimental values were cross‐compared. For protons, the obtained average absolute differences and root mean square (rms) errors for each comparison showed that the experimental chemical shifts of dextrorotatory and levorotatory 6β‐hydroxyhyoscyamines correlated well with the theoretical values calculated for the (3R,6R,2′S) and (3S,6S,2′S) configurations, respectively, whereas for ¹³C atoms the calculations were unable to differentiate between isomers. The nature of the relatively large chemical shift differences observed in nuclei that share similar chemical environments between isomers was asserted from the same calculations. It is shown that the anisotropic effect of the phenyl group in the tropic ester moiety, positioned under the tropane ring, has a larger shielding effect over one ring side than over the other one. Copyright © 2009 John Wiley & Sons, Ltd.     

几种苄基哌嗪衍生物13C NMR的计算研究

本文分别采用量子化学从头算Hatree-Fock方法和密度泛函B3LYP方法在6-311G++基组水平下对几种苄基哌嚷衍生物的13C NMR作了计算研究.结果表明两种方法计算得到的各苄基哌嗪衍生物中C原子化学位移的计算值与实验值之间均近似存在线性关系,其中采用考虑了电子相关作用的密度泛函方法计算时,各化合物中碳原子的化...     

Theoretical and experimental 13C and 15N NMR investigation of guanylhydrazones in solution

Experimental and theoretical ¹⁵N and ¹³C NMR data for the three nitrobenzaldehyde guanylhydrazones are reported. The theoretical data were obtained using sequential molecular dynamics/quantum mechanics methodology for the calculation of flexible molecules in a condensed phase, followed by the use of the GIAO/DFT method with the 6–311G** basis set. The experimental ¹⁵N chemical shifts for the guanylhydrazones are compared with the calculated shifts. Copyright © 2003 John Wiley & Sons, Ltd.     

Statistical analysis of (13)C and (15)N NMR chemical shifts from GIAO/B3LYP/6-311 + + G** calculated absolute shieldings

The (13)C and (15)N absolute shieldings of 28 compounds have been calculated at the GIAO/B3LYP/6-311 + + G** level to complete a collection of data already published. This has allowed us to devise new equations relating delta and sigma for these nuclei based on 461 points ((13)C) and 70(72) points ((15)N).     

Substituent effects on 13C chemical shifts of ketenimines: a GIAO/HF and DFT study

GIAO/HF and DFT methods were utilized to predict the ¹³C chemical shifts of substituted ketenimines. GIAO HF/6–311+G(2d,p) and B3LYP/6–311+G(2d,p) methods were applied on the optimized B3LYP/6–31G(d) geometries and ¹³C chemical shifts of C_α and C_β of substituted ketenimines were correlated with group electronegativities. HF and DFT calculations indicated that increasing substituent group electronegativity leads to increasing chemical shift of C_β of substituted ketenimines, whereas the C_α values decrease. Copyright © 2003 John Wiley & Sons, Ltd.