Density Functional Study on the Mechanism of Amadori Rearrangement Reaction

The reaction mechanism of amadori rearrangement in the initial stage of Maillard reaction has been investigated by means of density functional theory calculations in the gaseous phase and aqueous solution.Cyclic ribose and glycine were taken as the model in the amadori rearrangement.Reaction mechanisms have been proposed,and possibility for the formation of different compounds has been evaluated through calculating the relative energy changes for different steps of the reaction by following the total mass balance.The calculations reveal that the amadori rearrangement initialized via the intramolecular rearrangement,transferring one proton from N（3） to O（4） atom.In the next step,the second proton is also transferred from N（3） to O（4） atom,corresponding to the cleavage of C（4）-O（4） bond and the release of one water molecule.Then another proton is transferred from N（3） to C（5） atom via TS3 with the reaction barrier of 58.3 kcal·mol-1 after tunneling the effect correction calculated at the B3LYP/6-31＋G（d） level of theory,and this step is rate limiting for the whole catalytic cycle.Ultimately,the product is generated via keto-enolic tautomerization.Present calculation could provide insights into the reaction mechanism of Maillard reaction since experimental evaluation of the role of intermediates in the Maillard reaction is quite complicated.

A New Rearrangement Reaction of 2-Phenyl Substituted Benzothiazepine with Ethoxycarbonyl Carbene─Mechanism of the Reaction and Structure of the Product

2,3-Dihydro-2-phenyl-4-(4-methoxyphenyl)-1, 5-benzothiazepine reacts with ethoxycarbonyl carbene to give an unexpected compound 2,3-disubstituted-4H-1,4-benzothiazine Ⅲ. It was found to be a new rearrangement reaction and the structure of the product was confirmed by IR, NMR, MS.

STUDY ON THE REARRANGEMENT REACTION OF 5－AMINO－1－AMINOCARBONYL－1，2，AND ITS ANALOGUES

The discovery of a rearrangement reaction of 5-amino-1-arylaminocarbonyl-1,2,triazole(pyrszole)to 5-arylureylene-1,2,4-trazole and the mechanism for thisrearrangement reaction are presented. The rearrangement reaction could be attributed to athermodynamic energy preference leading to the predominant formation of 5-aryluretjlene1,2,4-triazole,as shown by molecular mechanics calculation with MMX Program.

Study on the Mechanism of the Rearrangement Reaction of 3-n-Butylphthalide by Deuterium-Labelling

By the Grignard reaction of 1,1-di-deutero-1-bromobutane with phthalaldehydic acid 1',1'-di-deutero-3-n-butyl phthalide was obtained, which underwent a rearrangement reaction using AlCl3 as catalyst in CS2 to give 1-methyl-5-carboxy-3,4-di-deutero-tetrahydronaphthalene. The mechanism was proposed to be a series of consecutive 1,2- hydride transfers rather than a direct 1,4-hydride transfer.

Unexpected Stereospecific Rearrangement-Addition Reaction of Trisubstituted Gibberellin Epoxides with Trimethylaluminium

A novel rearrangement-addition reaction of trisubstituted gibberellin epoxides with trimethylaluminium is reported. The reaction proceeds stereospecifically to give tertiary methyl alcohols. The possible mechanism for the reaction is also discussed.

THE REARRANGEMENT REACTION of 3-ALKYLPHTHALIDES

The rearrangement of 3-butylphthalide and its two homologues to 5- carboxyl- 1 -alkyltetrahydronaphthalene by 1,4 - hydride transfer and 3- propytphthalide to 4-carboxyl-1 -alkylindane by 1,3-hydride transfer in the presence of AICI3 were observed and the possible mechanism was discussed.

Rhodium-catalyzed Doyle-Kirmse rearrangement reactions of sulfoxoniun ylides

Doyle-Kirmse rearrangement reactions have received continuous attention as an important method for constructing complex chemical structures. Herein, we disclosed an efficient rhodium-catalyzed DoyleKirmse rearrangement reaction, which can simultaneously construct C–C bonds and C–X(X = S/Se) bonds using sulfoxonium ylides as starting materials to obtain sulfur-or selenium-containing compounds. This strategy is characterized by the safer and greener carbene precursor, high yields and broad substrate scope, possessing a wide range of application.

Estimation of kinetics parameters in Beckmann rearrangement of cyclohexanone oxime using genetic algorithm

Beckmann rearrangement mechanism of cyclohexanone oxime, based on the characteristic of self-catalyzed reaction and polymorphism was proposed. According to the suggested mechanism, the basic approach was the rearrangement of OXH+ while the SO3 acts as dehydrating agent and OXSO3 can turn to CPLSO3 ultimately. Considering self-catalyzed reaction between OXSO3 and CPLH+, kinetic model for Beckmann rearrangement was established. Corresponding parameters were estimated by using float genetic algorithm （GA） and simulation results agree well with the experimental data below -19.3℃. Industrial equipment was simulated and analyzed. Effects of key process parameters such as molar ratio of sulfuric acid to oxime and circulation ratio on the residual oxime are also discussed. The results show that the caprolactam exists as CPLH+ finally in oleum and the minimum molecular ratio of sulfuric acid to oxime can be 0.5 theoretically.

Gene Rearrangement Analysis of Orbital Lymphoid Infiltrating Disorders

Purpose:To determine whether the use of polymerase chain reaction for B-cell gene rearrangement in patients with orbital lymphoid infiltrate disorders could be useful in the diagnosis of lymphoma,especially,in differentiating benign lesion from malignant one.Methods:In addition to clinical,pathological,and immunohistochemical evaluations,48 cases of orbital lymphoid infiltrate disorders were examined for immunoglobulin heavy(IgH)gene rearrangement by means of PCRto amplify the FR3region with formalin-fixed and paraffin-embedded tissues.Results:Gene rearrangement in the third frame-work of the IgH region was detected in specimens obtained from15cases of malignant lymphoma,4of reactive lymphoid hyperplasia and3of orbital pseudotumor.All of these patients showed a discrete band(100bp)which reflected monoclonal proliferation of B lymphocytes.5cases of malignant lymphoma,6ofreactive lymphoid hyperplasia and 15of orbital pseudotumor did not show a discrete band on PCR.Conclusions:The FR3 region gene rearrangement of Ig heavy in patients with orbital lymphoid infiltrate disorders may be an additional diagnostic tool in differentiating benign from malignant lymphoid diseases and in offering a useful adjunct for diagnosis in difficult or unclear cases.It is a reliable and practical method of gene diagnosis in orbital lymphoid infiltrate disorders and helps to identify the molecular mechanism of malignant lymhoma.Eye Science2000;16:15-21.

Detection of IgH and T-cell receptor gene rearrangement in leukemia by PCR amplification and its clinical application

PCR amplification was used to detect immunoglobulin heavy chain (IgH), T-cell receptor (TCR)Vγ1-Jγ, Vδ2-Dδ 3 rearranged genes in 45 cases of acute lymphoblastic leukemia (ALL) and IgH gene rearrangement in 41 cases acute nonlymphoblastic leukemia (ANLL). The positive percentage of the IgH, TCR Vγ1-Jγ and Vδ 2-Dδ3 gene rearrangement was found to be 66. 7%, 62.2%, and 35. 6%, respectively in 45 ALL patients. Multiple rearranged IgH gene bands were found in 8 (26. 7% ) out of 30 ALL patients with IgH gene rearrangement. IgH gene rearrangemens were found in 7 (17. 1% ) out of 41 ANLL patients. ALL patients with positive IgH rearranged gene were with B cell and those with positive TCR Vγ1-Jγ gene rearrangements and with negative IgH rearranged gene were with T-ALL,those with positive both IgH and TCR Vδ2-Dδ3 rearranged genes mostly were with preB-ALL. The complete remission (CR) rate was low in ALL patients with multiple rearranged heavy chains and ANLL patients with IgH gene rearrangement, who were more likely to have a clinical relapse, which may be due to clonal evolution. In complete remission (CR) patients, the cytologic relapse fell behind postive PCR results for an average periods of 7. 2 weeks (range 2 to 23 weeks). Using PCR to detect rearranged genes could be helpful in determining the efficacy of chemotherapy, predicting clinical relapse, assisting gene typing and predicting prognosis.

Bcl-2 GENE REARRANGEMENT DETERMINED BY PCR AS AMEAN TO DETECT MINIMAL RESIDUAL DISEASE INMALIGNANT LYMPHOMAS

Objective: To develop a sensitive method to detect minimal residual disease and to elucidate the significance of bcl-2 gene rearrangement in diagnosis and treatment of malignant lymphoma. Methods: Using polymerase chain reaction (PCR) to detect bcl-2 gene rearrangement and using serial dilution method to define the sensitivity of PCR. Results: In 9 different malignant lymphoma cell lines, Su-DHL-4 and Su-DHL-6 were shown bcl-2(MBR)/JH rearrangement, the sensitivity of PCR was 1:105. In 16 patients with follicular lymphoma, the peripheral blood and bone marrow were PCR positive in 4 cases both at initial diagnosis and after complete remission. Conclusion: Detection of bcl-2 gene rearrangement by PCR provides a sensitive and specific assay of minimal residual disease. It is helpful to improve staging of disease, prognosis and evaluation of the treatment results.

The Rearrangement of 2-Benzothiazolylthioacetyl Hydrazide in Synthesis of s-Triazolo[3,4-b]benzothiazole-3-thiol

The rearrangement reaction of 2-benzothiazolylthioacetyl hydrazide 1 with potassium hydroxide and carbon disulfide in ethanol to produce s-triazolo[3, 4-b]benzothiazole-3-thiol 3 was described. 3 also can be obtained from 2-benzothiazolylhydazine 2 and the two methods for getting 3 were compared. Mannich reaction of compounds 3 was reported too.

Analysis of gene rearrangements of antigen receptors of nonHodgkin＇s lymphoma of T－cell lineage

The gene rearrangement of βand γchain of T-cell receptors (TCR) was detected in 13 cases of non-Hodgkin's lymphoma with T-cell immunophenotype with Southern blot and PCR. Clonally rearranged.TCR βgene was seen in 11 cases out of the 13 and rearranged TCR γgene in 12. These facts suggest that clonal rearrangement of antigen receptors is a sensitive and specific marker to establish the T-cell monoclonality and lineage and a useful adjunct to morphological diagnosis and immunophenotyping.

Beckmann重排反应的综合性实验设计与教学应用

Beckmann反应是含有羰基的醛、酮与羟胺反应生成有机肟,在催化剂作用下发生重排,在有机合成中具有重要意义。针对实验教学中有机肟Beckmann重排反应的实验原理直观性不足、反应机理佐证性欠缺等问题,通过二苯甲酮与盐酸羟胺反应生成二苯甲酮肟,多聚磷酸催化分子重排反应生成苯甲酰基苯胺为案例,交叉运用无机化学、分析化学、仪器分析的知识和实验技能,测定阶段产物和终产物的熔点、红外光谱、核磁共振谱并表征其结构,将宏观理化性质与微观结构相结合,解析和验证反应机理,达到Beckmann重排反应实验原理直观、反应机理佐证完善的结果,实验的综合设计与交叉创新提升了Beckmann重排实验的教学效果,并激发学生的创新意识。本文既可为肟类Beckmann重排反应的综合性、设计性实验提供借鉴,也可为教材及实验的改进提供有价值的参考。

基于DFT的环己酮肟液相贝克曼重排机理研究

为了研究质子酸催化的环己酮肟液相贝克曼重排反应机理,使用密度泛函理论中的B3LYP-D3/6-31G(d)方法研究了反应中的过渡态内禀反应坐标,并使用SMD隐式溶剂模型模拟了液相环境。利用前线分子轨道和表面静电势确定了反应的主导因素,通过频率计算获得了过渡态和中间体的Gibbs自由能,确定了速率控制步骤。重排反应不可逆,而水解可逆,环己酮肟先进行双分子重排,然后进行反向水解。低温下,少量水对反应影响较小,提出了环己酮肟最有可能发生双分子重排-水解反应路径。在乙腈溶剂中,静电效应是环己酮肟与质子发生亲电反应的主导因素,局部亲电/亲核性是质子化环己酮肟与水或环己酮肟发生亲核反应的主导因素。本研究有助于深入理解环己酮肟液相贝克曼重排过程,并为避免发生副反应的固体催化剂设计提供理论基础。

典型频哪醇重排反应的机理及基团迁移规律的研究——一个研究型计算化学实验

频哪醇重排是本科有机化学课程的重要内容,但学生对重排机理、区域选择性和基团迁移规律不能很好地理解掌握。为了加强学生对频哪醇重排反应的理解,我们设计了一个利用计算化学方法解决有机化学问题的实验。通过直观的图像和具体的数据清楚地展现出:能形成稳定碳正离子中间体的底物主要以分步重排机理进行,而不能形成稳定中间体的底物则按协同重排机理进行。计算结果验证了反应的区域选择性取决于邻二醇质子化羟基的位置以及基团的迁移能力,明确了基团迁移能力的顺序为氢>芳基>烷基,并从微观角度对其进行了合理解释。

质谱中气相Smiles重排反应的研究进展

人名反应基于反应机理对复杂的有机化学反应进行了梳理和总结,极大地促进了有机化学研究,并方便了化学家们的交流。在质谱领域,气相人名反应的类型并不多,常见的包括麦氏重排(McL)和逆狄尔斯-阿尔德(RDA)反应等。这些广为人知的气相人名反应由于具有显著的结构特异性,成为了质谱结构解析的有力工具。随着软离子化结合多级质谱技术的发展,越来越多新型的气相反应被发现和研究,其中气相Smiles重排反应因其复杂而有趣的骨架重排而备受质谱学家和化学家关注。气相Smiles重排能够引起化合物骨架的变化,导致一些意想不到的中性丢失。与凝聚相Smiles重排反应相比,气相Smiles重排反应不受五元环过渡态形式的限制,也无需碱性条件的引发。这正是气相离子反应的特点,但同时,更多可能的裂解途径也给解谱带来了挑战。系统总结了近年来报道的质谱中气相Smiles重排反应,分析了化合物结构、离子化方法以及电荷状态对气相Smiles重排反应的影响,为基于质谱中气相Smiles重排反应进行化合物结构解析,以及发现化合物在凝聚相条件下的类似反应提供了线索和信息。

Sequence [2,3]-Sigmatropic Rearrangement: One-Pot Synthesis of Proparggyl Allenylamines

Allenes,served as highly sought-after building blocks,are an indispensable component of synthetic chemistry.Their utility in modulating the chemical,physical,and pharmaceutical properties of organic compounds make allenes a desirable choice in various applications.Here,we report a facile method for the atom-economical synthesis of propargyl allenylamines via an underdeveloped[2,3]-sigmatropic rearrangement.Our strategy employs easily accessible propargylamines as starting materials,which are first converted into propargyl ammonium salts,followed by a base-promoted[2,3]-sigmatropic rearrangement.This one-pot,two-step reaction proceeds in the absence of transition metals,displays a very broad scope,and does not require the introduction of the electron-withdrawing group into the starting materials.

On-Surface Synthesis of Anthracene-Fused Zigzag Graphene Nanoribbons from 2,7-Dibromo-9,9′-bianthryl Reveals Unexpected Ring Rearrangements

On-surface synthesis has emerged as a powerful strategy to fabricate unprecedented forms of atomically precise graphene nanoribbons(GNRs).However,the on-surface synthesis of zigzag GNRs(ZGNR)has met with only limited success.Herein,we report the synthesis and on-surface reactions of 2,7-dibromo-9,9′-bianthryl as the precursor towardπ-extended ZGNRs.Characterization by scanning tunneling microscopy and high-resolution noncontact atomic force microscopy clearly demonstrated the formation of anthracene-fused ZGNRs.Unique skeletal rearrangements were also observed,which could be explained by intramolecular Diels-Alder cycloaddition.Theoretical calculations of the electronic properties of the anthracene-fused ZGNRs revealed spin-polarized edge-states and a narrow bandgap of 0.20 eV.