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对手性唑硼烷催化3,3-二甲基丁酮-2不对称还原反应机理进行了从头算研究.结果表明,该不对称还原反应是放热的.反应经历了催化剂-硼烷加合物、催化剂-硼烷-酮加合物、含B-O-B-N四元环的催化剂-烷氧基硼烷加合物的生成,以及催化剂-烷氧基硼烷加合物的离解并再生催化剂等过程.在催化剂-硼烷-酮加合物经氢转移而生成催化剂-烷氧基硼烷加合物的过程中,氢转移与B-O-B-N四元环的形成是协同进行的.氢转移是还原反应的控制步骤.氢转移过渡态具有扭曲的椅式结构,所决定的还原产物是与实验相吻合的R手性醇. 相似文献
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对手性噁唑硼烷催化3,3-二甲基丁酮-2不对称还原反应机理进行了从头算研究.结果表明,该不对称还原反应是放热的.反应经历了催化剂-硼烷加合物、催化剂-硼烷-酮加合物、含B-O-B-N四元环的催化剂-烷氧基硼烷加合物的生成,以及催化剂-烷氧基硼烷加合物的离解并再生催化剂等过程.在催化剂-硼烷-酮加合物经氢转移而生成催化剂-烷氧基硼烷加合物的过程中,氢转移与B-O-B-N四元环的形成是协同进行的.氢转移是还原反应的控制步骤.氢转移过渡态具有扭曲的椅式结构,所决定的还原产物是与实验相吻合的R手性醇. 相似文献
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不对称硼催化反应的理论研究(Ⅰ)——恶唑硼烷催化苯基乙酮还原反应的对映体选择性机理 总被引:2,自引:0,他引:2
用AM1方法研究了恶唑硼烷催化苯基乙酮还原反应的对映体选择性机理,结果表明,在此硼催化剂的作用下,苯基乙酮还原的对映体产物主要是R构型,其主要原因是两种对映体的催化过渡态的活化能相差较大所致。用过渡态活化理论计算所得光学产率e.e.=95%,计算结果与实验一致。 相似文献
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氨基硼烷化合物近年来在储氢材料的开发以及在有机合成中的应用非常广泛。本文综述了氨基硼烷的合成及其作为储氢材料的研究进展,以及近十几年来氨基硼烷在有机合成中作为还原试剂、在不对称还原反应中作手性催化剂及其他反应中的应用研究进展。指出加入金属氢化物制备的金属氨硼烷具有较优的放氢性能、可再生氨硼烷储氢材料的开发和制备是储氢材料新的发展方向;发展清洁高效的绿色还原体系和高选择性的手性氨硼烷催化剂是氨硼烷研究领域的新热点;氨硼烷试剂在储氢材料开发和绿色还原试剂领域具有潜在的实际应用价值。 相似文献
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Hikmet Aĝirbaş Selahattin Güner 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):257-263
Abstract 4-Substituted-2,3-1H-benzoxazine-1-thiones were prepared by the treatment of the corresponding benzoxazine-1-ones with P2S5. The thermal rearrangement of 4-substituted-2.3-1H-benzoxazine-1-thiones, catalysed by metallic copper, yielded 4-substituted-2.3-1 H-benzthiazine-1-ones. 相似文献
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综述了凤尾蕨科植物中分离得到的1H 茚 1 酮类倍半萜的化学合成、化学转化、生物活性以及1 茚酮倍半萜的二聚体化合物和三环1 茚 1 酮倍半萜等方面的研究情况. 相似文献
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采用不同电压高压芒刺静电场对小鼠进行全身辐射,荧光免疫流式细胞术检测蛋白表达量的变化.通过时程/量效研究不同电压高压芒刺静电场对细胞表面分子LFA-1和ICAM-1的影响.剂量效应结果表明,LFA-1和ICAM-1在10~20 kV之间处理组的表达量明显高于对照组(P<0.01);在30 kV以上电压表达量明显降低(P<0.05);时间进程研究结果表明,处理后2 h开始实验组表达量与对照组相比差异显著,一直持续到24 h.不同电压高压芒刺静电场可引起ICAM-1和LFA-1不同的生物效应,二者的相互作用在免疫调节反应中发挥重要功能. 相似文献
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P. Manivel Ashok Sharma T. Maiyalagan M. R. Rajeswari F. Nawaz Khan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):387-393
A series of 1H-isochromen-1-one derivatives and their thio analogues were synthesized by thionation using Lawesson's reagent for evaluation of their cytotoxic effect on cancer cells. The effect of these derivatives was tested on the growth of human epidermoid carcinoma A431 cell line by MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] colorimetric assay. MTT assay revealed that these new compounds are potent inhibitors of cell growth. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
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Tom Sundermann 《合成通讯》2014,44(11):1641-1648
A novel method for the synthesis of 1-tetrazolylalkan-2-amines and -carbamates via tert-butyl aziridine-1-carboxylates is described. 相似文献
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Tran Dinh Phien Liubov E. Kuzmina Elena N. Suslova Bagrat A. Shainyan Sergey A. Shlykov 《Tetrahedron》2019,75(22):3038-3045
Molecular structure and conformational equilibria of 1-methoxy- 1 and 1-hydroxy-1-phenylsilacyclohexanes 2 were studied by quantum chemical (QC) calculations and combined gas electron diffraction/mass spectrometry (GED/MS). Both molecules may exist in 5 or 6 forms, differing from each other by the substituents' position: (i) axial or equatorial and (ii) rotational orientation relative to the six-membered ring frame. The contribution of axial forms of both compounds varies from 35 to 60% depending on the theoretical method applied. From the GED data, the summarized molar fractions of the conformers were found to be Phax:Pheq = 70(15):30(20) and 50(20):50(20)% which corresponds to ΔG = Gax–Geq = ?0.55(46) and 0.00(56) kcal/mol, for compound 1 and 2, respectively. The concentration of the Phax forms of 1-phenyl-1-(X)-silacyclohexanes (X = H, HO, Me, MeO and Me2N) increases with the size of the second substituent at the silicon atom: 38(10)<50(20)<58(15)<70(15) <80(15)%. 相似文献
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Andrzej J. Treszczanowicz Teresa Treszczanowicz Tomasz S. Pawłowski Teresa Kasprzycka-Guttman 《Journal of solution chemistry》2004,33(8):1049-1060
Excess molar volumes, V
E, are reported for binary mixtures of 1-hexanol with the homologous C6, C7, C8, and C10 1-alkenes at 25°C. In this series of mixtures, the V
E values vary as a function of mole fraction from positive–negative sigmoid shaped curves exhibiting a very small positive lobe in the dilute alkanol region for the shortest chain 1-alkene to positive values over the whole concentration range for the longer chain 1-alkene. The partial molar excess volumes, V
i
E, were calculated for the components over the whole concentration range. The partial molar volume of 1-hexanol in the 1-hexene system shows a large and sharp minimum and in the 1-decene system is positive over the whole concentration range. The modified model [Treszczanowicz et al., J. Solution Chem.
31, 455 (2002) originally proposed by Treszczanowicz and Benson Fluid Phase Equilibr.
23, 117 (1985)] was used for the interpretation and prediction of the reported data. The model describes qualitatively the variation of V
E with the length of the molecule and concentration as a result of superposition of the contributions of association, free volume, and nonspecific interactions. 相似文献