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Products from the reaction of C60F18 with sarcosine and aldehydes: the Prato reaction C60F18与肌氨酸和醛反应的产物:普拉托反应
Pub Date : 2002-12-17 DOI: 10.1039/B106877F
Xian‐Wen Wei, A. G. Avent, O. Boltalina, J. M. Street, R. Taylor
Various pyrrolidinofullerenes (both mono- and bis-addition products) have been isolated from the reaction between toluene solutions of C60F18, N-methyl-2-aminoethanoic acid (sarcosine) and either formaldehyde or benzaldehyde. Both mono- and bis-addition products were obtained and either partially of fully characterised. The main mono-addition product from the reaction with formaldehyde was also obtained from reactions with the other aldehydes, indicating that formaldehyde may be present in sarcosine, or generated from it through in situ oxidation by the fullerene. The main mono-addition product from reaction of C60F18 with toluene solutions of sarcosine and benzaldehyde was obtained also in the absence of benzaldehyde. This anomaly was traced to the presence of benzaldehyde (0.05%) in HPLC grade toluene, which may be increased by oxidation of toluene during the reaction conditions.
从C60F18 - n -甲基-2-氨基乙醇酸(肌氨酸)的甲苯溶液与甲醛或苯甲醛反应中分离出多种吡咯烷二富勒烯(单加成和双加成产物)。得到了单加成产物和双加成产物,并进行了部分或完全表征。与甲醛反应的主要单加成产物也可以从与其他醛的反应中得到,这表明甲醛可能存在于肌氨酸中,或者由它通过富勒烯的原位氧化而产生。在不含苯甲醛的情况下,C60F18与肌氨酸和苯甲醛的甲苯溶液反应得到了主要的单加成产物。这种异常可以追溯到HPLC级甲苯中存在苯甲醛(0.05%),这可能是由于反应条件下甲苯的氧化而增加的。
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引用次数: 2
Small steric effects in isolated molecules: alkyl-substituted benzonitriles 分离分子中的小空间效应:烷基取代的苯并腈
Pub Date : 2002-12-17 DOI: 10.1039/B104856M
O. Exner, S. Böhm, M. Decouzon, J. Gal, P. Maria
A series of seven alkyl-substituted benzonitriles was investigated as a model for small steric effects (van der Waals tension) excluding any steric inhibition due to resonance. The energies were calculated at a B3LYP/6-311+G(d,p) level and the gas-phase basicities of some compounds were measured by Fourier-transform ion cyclotron resonance. Substituent effects were evaluated separately for neutral molecules and protonated forms by means of isodesmic reactions, and dissected into polar and steric effects by comparing ortho and para derivatives. One or two ortho methyl groups have a relatively small steric effect operating almost exclusively in the protonated form which leads to weakened basicity. An ortho tert-butyl group exerts a strong steric effect both in the protonated and nonprotonated forms, manifested also in a rather strong distortion of geometry. The effect on basicity is then a small difference of two large values and is base strengthening. Acid–base properties are in such cases a poor measure of substituent effects and cannot be interpreted in simple terms.
研究了一系列七个烷基取代苯并腈作为小空间效应(范德华张力)的模型,排除了共振引起的任何空间抑制。计算了B3LYP/6-311+G(d,p)能级的能量,并用傅里叶变换离子回旋共振测量了部分化合物的气相碱度。通过等密度反应分别对中性分子和质子化形式的取代基效应进行了评价,并通过比较邻位衍生物和对位衍生物,将取代基效应分解为极性和立体效应。一个或两个邻甲基具有相对较小的空间效应,几乎完全以质子化形式运作,导致碱度减弱。邻位叔丁基在质子化和非质子化形式下都有很强的空间效应,并表现为很强的几何畸变。对碱度的影响是两个大值的小差,是碱度强化。在这种情况下,酸碱性质是取代基效应的一个很差的度量,不能用简单的术语来解释。
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引用次数: 1
15N NMR spectra, tautomerism and diastereomerism of 4,5-dihydro-1H-1,2,3-triazoles 1,2,3- 4,5-二氢- 1h -1,2,3-三唑的15N核磁共振波谱、互变异构和非对映异构
Pub Date : 2002-12-17 DOI: 10.1039/B107326E
K. Banert, Jens Lehmann, H. Quast, G. Meichsner, D. Regnat, B. Seiferling
Despite the great number of 4,5-dihydro-1H-1,2,3-triazoles synthesized, 15N NMR data of these heterocycles are extremely rare. The aim of this paper is to present such data and examples of their application. The compounds investigated have been synthesized according to the given references or procedures. Their 15N NMR spectra were measured at natural abundance. For some compounds, the chemical shift assignments were confirmed with the help of 15N labelled material. The influences on 15N chemical shifts of substitution pattern, solvent and concentration were investigated. Additionally, some lanthanide induced shift (LIS) investigations were performed. 13C labelled compounds were employed as tools to provide the assignment of tautomeric structures.
尽管合成了大量的4,5-二氢- 1h -1,2,3-三唑,但这些杂环的15N NMR数据却极为罕见。本文的目的是介绍这些数据及其应用实例。所研究的化合物是根据给定的参考文献或程序合成的。它们的15N核磁共振谱以自然丰度测量。对于一些化合物,化学位移赋值在15N标记材料的帮助下得到了确认。考察了取代模式、溶剂和浓度对15N化学位移的影响。此外,还进行了一些镧系元素诱导位移(LIS)的研究。13C标记的化合物被用作工具来提供互变异构结构的分配。
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引用次数: 1
EPR and computational studies of the formation and beta-scission of cyclic and acyclic dialkoxyalkyl radicals 环和非环二氧烷基自由基形成和裂解的EPR和计算研究
Pub Date : 2002-12-17 DOI: 10.1039/B106140M
Alistair J. Fielding, P. Franchi, B. P. Roberts, Teika M. Smits
EPR spectroscopy and density functional theory have been applied to study the formation and subsequent β-scission of a series of dialkoxyalkyl radicals. Abstraction of hydrogen by photochemically-generated tert-butoxyl radicals from acyclic acetals R1O(R2O)CHR3, and from cyclic analogues derived from diols, takes place mainly from the acetal carbon atom to give radicals of the type R1O(R2O)ĊR3 and relative rates of abstraction have been determined in competition experiments. When R3 = phenyl or vinyl, the activating influence of these substituents on hydrogen-atom abstraction is smaller than might be expected, probably because delocalisation of the unpaired electron on to the unsaturated group comes at the expense of planarisation at Cα, in opposition to the natural pyramidalising tendency of the two α-alkoxy groups. Absolute rate constants and Arrhenius activation parameters for β-scission of R1O(R2O)ĊR3 have been determined by a steady-state EPR method and the results can be understood in terms of angle-strain and stereoelectronic effects. β-Scission of selected cyclic dialkoxyalkyl radicals that carry a phenyl or vinyl substituent at the radical centre has been investigated using density functional theory at the UB3LYP/6-31G(d,p) level. Computed activation parameters are in good agreement with the experimental results, where comparison is possible. Both experiment and theory indicate that benzylic 2-phenyl-1,3-dioxan-2-yl radicals undergo β-scission more readily than the corresponding allylic 2-vinyl-1,3-dioxan-2-yl radicals.
应用EPR光谱和密度泛函理论研究了一系列二氧烷基自由基的形成和随后的β-裂解。从无环缩醛r10 (R2O)CHR3和从二醇衍生的环类似物中,光化学生成的叔丁氧基自由基主要是从缩醛碳原子中提取氢,得到r10 (R2O)ĊR3型自由基,相对提取速率已在竞争实验中确定。当R3 =苯基或乙烯基时,这些取代基对氢原子抽离的激活影响比预期的要小,这可能是因为未配对电子离域到不饱和基团上是以牺牲Cα的平面化为代价的,这与两个α-烷氧基的自然金字塔化倾向相反。用稳态EPR法测定了r10 (R2O)ĊR3 β-断裂的绝对速率常数和Arrhenius活化参数,结果可以从角-应变和立体电子效应的角度来理解。在UB3LYP/6-31G(d,p)水平上,利用密度泛函理论研究了在自由基中心携带苯基或乙烯基取代基的环二氧基自由基的β-断裂。计算的活化参数与实验结果吻合较好,可以进行比较。实验和理论均表明,苯基2-苯基-1,3-二恶烷-2-基自由基比对应的烯丙基2-乙烯基-1,3-二恶烷-2-基自由基更容易发生β-断裂。
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引用次数: 5
Inverse Wittig reaction of oxaphosphetenes formed by the [2+2] cycloaddition of arylphosphine oxides and dimethyl acetylenedicarboxylate (DMAD) 芳基膦氧化物与二甲基乙炔二羧酸酯(DMAD)[2+2]环加成形成的氧膦烯的逆Wittig反应
Pub Date : 2002-12-17 DOI: 10.1039/B108675H
G. Keglevich, Henrietta Forintos, T. Körtvélyesi, L. Tőke,
The intermediate oxaphosphetenes 2 formed by the novel cycloaddition of the PO group of arylphosphine oxides 1 and the acetylene moiety of DMAD are stabilised by an inverse Wittig reaction to afford the corresponding stabilised phosphonium ylide 3.
由芳基膦氧化物1的PO基团和DMAD的乙炔部分的新型环加成而形成的中间氧磷烯2通过逆Wittig反应稳定,得到相应的稳定的磷酰化3。
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引用次数: 11
Condensation of triformylmethane with adenosine: novel cyclic adducts derived from 1,3-dicarbonyl compounds 三甲酰甲烷与腺苷的缩合:从1,3-二羰基化合物中衍生的新型环状加合物
Pub Date : 2002-12-17 DOI: 10.1039/B104790F
K. Neuvonen, N. Koissi, H. Lönnberg
Condensation of triformylmethane (TFM) with adenosine has been studied in pyridine and aqueous dioxane. One 1 ∶ 1 (2) and two 2 ∶ 1 (6 and 7) TFM–adenosine adducts were isolated. The structural assignment of these products by 1H and 13C NMR and UV spectroscopy and MS spectrometry suggested that the appearance of the 2 ∶ 1 adducts is connected to a competitive self-condensation of TFM, the stable end product of which is benzene-1,3,5-tricarbaldehyde. The intermediates on the reaction pathway can be reacted with adenosine affording a new procedure for nucleic acid base modification. The mechanisms of formation and the role of intramolecular hydrogen bonding in stabilization of cyclic adenosine adducts are discussed.
研究了三甲酰甲烷(TFM)与腺苷在吡啶和二氧六环水溶液中的缩合反应。分离得到1个1∶1(2)和2个2∶1(6和7)tfm -腺苷加合物。通过1H、13C NMR、紫外光谱和质谱对产物进行结构表征,表明2∶1加合物的出现与TFM的竞争性自缩合反应有关,其稳定的终产物为苯-1,3,5-三乙醛。反应途径上的中间体可与腺苷反应,为核酸碱基修饰提供了新的途径。讨论了环腺苷加合物的形成机理和分子内氢键在稳定环腺苷加合物中的作用。
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引用次数: 1
Diastereocontrolled synthesis of hydroxylated lactams 羟基内酰胺的非对映控制合成
Pub Date : 2002-12-17 DOI: 10.1039/B108056N
M. Andrews, A. Brewster, M. Moloney
Highly diastereoselective reductions and organometallic additions in bicyclic lactams have been observed, which appear to result either from a stereoelectronic interaction of the pyramidalised nitrogen lone pair or from steric interactions in the bicyclic system. These products can be readily deprotected to give hydroxylated lactams.
在双环内酰胺中观察到高度非对映选择性的还原和有机金属添加,这似乎是由锥体化氮孤对的立体电子相互作用或双环系统中的立体相互作用引起的。这些产物可以很容易地去保护,得到羟基内酰胺。
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引用次数: 2
Phenyl group acceleration of [1,4] carbon-to-oxygen silicon-mediated elimination–rearrangement in β-silyl sulfones. Synthesis of O -silylated cinnamyl alcohols β-硅基砜中[1,4]碳-氧-硅介导的消除重排的苯基加速。O -硅基化肉桂醇的合成
Pub Date : 2002-12-17 DOI: 10.1039/B109805E
S. Menichetti, C. Stirling
A very fast [1,4] carbon-to-oxygen silicon migration-rearrangement leading to O-silylated cinnamyl alcohols occurs when the carbanion generated from sulfone 1 is reacted with carbonyl compounds. The mandatory role of the adjacent phenyl ring in this process is demonstrated when compared to the behaviour of the corresponding unsubstituted sulfone 3.
当砜1生成的碳离子与羰基化合物反应时,碳到氧硅的快速迁移重排导致o-硅基化肉桂醇发生。与相应的未取代砜3的行为相比,相邻苯环在这一过程中的强制作用得到了证明。
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引用次数: 2
Vibrational spectroscopy of a tetraureidocalix[4]arene based molecular capsule 四金枝[4]芳烃基分子胶囊的振动光谱研究
Pub Date : 2002-12-17 DOI: 10.1039/B108055P
J. Dormann, A. Ruoff, J. Schatz, M. Vysotsky, V. Böhmer
Structural models for self-assembled dimers composed of two urea calix[4]arenes which entrap benzene or cyclohexane are developed using Fourier transform infrared (FTIR) spectroscopy. Based on the host–guest ratio determined by 1H NMR spectroscopy in solution, and confirmed for the solid state by a thermogravimetric analysis, it is possible to prove by a comparison of the FTIR data of host, guest, complex and model compounds, that the capsule is held together by a cyclic array of weak and strong hydrogen bonds between the urea units attached at the wide rim of the calixarenes. The dimerization of the two urea units leads to a loss of symmetry, and an averaged C4 symmetrical arrangement is probable. Guest molecules, such as benzene or cyclohexane, are enclosed inside the container rotating fast on the IR timescale around a longitudinal axis of the guest. From the observed splitting of absorption bands upon dimerization and inclusion it follows that either two crystallographically independent types of capsules exist in the crystal lattice or that the guests are occupying two major orientations in the capsule. As indicated by a higher complexation induced shift for cyclohexane, this guest exhibits a tighter interaction with the host molecules compared to benzene.
利用傅里叶变换红外光谱(FTIR)建立了由两个脲杯[4]芳烃组成的自组装二聚体的结构模型。根据溶液中1H核磁共振谱测定的主客体比,以及固态热重分析证实的主客体比,通过对主客体、配合物和模型化合物的FTIR数据的比较,可以证明胶囊是由连接在杯芳烃宽边缘的尿素单元之间的弱氢键和强氢键的循环阵列结合在一起的。两个尿素单元的二聚化导致对称性的丧失,平均C4对称排列是可能的。客体分子,如苯或环己烷,被封闭在容器内,在红外时间标上围绕客体的纵轴快速旋转。从观察到的吸收带在二聚化和包合时的分裂可以得出结论,在晶格中存在两种晶体学上独立的胶囊类型,或者来宾占据了胶囊中的两个主要方向。正如环己烷的高络合诱导位移所表明的那样,与苯相比,该客体与宿主分子的相互作用更紧密。
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引用次数: 1
Reductive cleavage of N-substituted aromatic amides as tert-butyl acylcarbamates n -取代芳香酰胺还原裂解为叔丁基氨基甲酸酯
Pub Date : 2002-12-17 DOI: 10.1039/B107330N
U. Ragnarsson, L. Grehn, H. Maia, L. Monteiro
Synthetic and spectroscopic details relating to a set of heteroaromatic N-benzyl carboxamides and in particular the corresponding tert-butyl acylcarbamates are reported. These compounds were required to study the postulated effect of various heterocycles (pyridine and pyrazine with and without condensed benzene rings) on the cleavage of acyl–N bonds by reduction. All compounds were initially characterized by cyclic voltammetry (CV) which indicated various degrees of facilitated reduction, reflecting a direct influence of the heterocyclic component. Selected acylcarbamates were studied with respect to acyl–N bond cleavage by mild reducing agents, and selectively deacylated by activated aluminium and sodium borohydride. Conversion to acylcarbamates followed by reduction might therefore be a mild, efficient two-step procedure to effect cleavage of amides, allowing isolation of carbamates and with sodium borohydride also the corresponding alcohols.
本文报道了一组异芳n -苄基羧酰胺,特别是相应的叔丁基氨基甲酸酯的合成和光谱细节。这些化合物被用来研究各种杂环(吡啶和吡嗪,有或没有凝聚苯环)对酰基- n键的还原裂解的假设影响。所有化合物最初都用循环伏安法(CV)表征,表明不同程度的促进还原,反映了杂环成分的直接影响。用温和还原剂研究了选定的氨基甲酸酯对酰基- n键的裂解,并用活性铝和硼氢化钠选择性地使其脱酰。因此,转化为氨基甲酸酯,然后还原可能是一种温和、有效的两步程序,可以实现酰胺的裂解,从而分离氨基甲酸酯,并与硼氢化钠分离相应的醇。
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引用次数: 21
期刊
Journal of The Chemical Society-perkin Transactions 1
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