以镍为阴极由二氧化碳与芳香酮电合成α-羟基羧酸

室温下,在一室电解池中,以n-Bu4NBr-DMF作电解质、镍为阴极、铝为阳极,恒电流电解二氧化碳与芳香酮（苯乙酮、对二苯甲酮、6-甲氧基-2-萘乙酮、4-甲基苯乙酮和4-甲氧基苯乙酮）,可以得到相应的α-羟基羧酸（产率56%-90%）。实验结果显示,阴极材料、芳香族酮的结构以及电解条件（如电量、底物浓度、导电盐、溶剂和二氧化碳压力等）对目标产物的产率有很大影响;反应系统中质子剂（水）的存在将导致副产物频哪醇的生成。本文还根据循环伏安实验和合成实验结果简要地讨论了反应机理。     

重氮盐与肟的反应 Ⅱ.某些芳香醛、酮、腈的合成

芳香族重氮盐可与肟反应,得到芳香醛和芳香酮^[1-4]。本文报道利用重氮盐与肟的反应合成对-乙酰基苯甲醛(1a)、对-乙酰氨基苯甲醛(1b)、对-溴苯乙酮(1c)、对-硝基苯乙酮(1d)、邻-氯苯甲腈(2a)以及2,4-二硝基苯甲腈(2b)的实验结果。这些化合物均为有机合成原料及重要中间体。     

一种使用1,3-二溴-5,5-2甲基苯乙酮α-溴代新方法

报道了使用1,3-二溴-5,5-二甲基海因和对甲苯磺酸在甲醇中和20～60 ℃的温和条件下合成α-溴代苯乙酮的新方法. 对位和间位取代的苯乙酮获得了高的产率; 而在同样条件下, 邻位硝基苯乙酮没有发生反应.     

芳香酮与芳香醛及芳香胺的Mannich反应

醛、酮与芳香醛及芳香胺的 Mannich 反应,文献[1]曾报道在 HCl-EtOH 溶液中苯乙酮及甲醛与芳香胺的 Mannich 反应。本文在此基     

环糊精介入酵母细胞催化芳香酮的不对称还原反应

以苯乙酮、苯丙酮、4'-甲基苯乙酮和4'-氯苯乙酮为底物,研究了酵母细胞催化芳香酮的不对称还原反应,分别考察了添加剂β-环糊精和羟丙基-β-环糊精对酵母细胞催化芳香酮的不对称还原反应的影响,结果表明芳环上取代基的空间效应和电子效应对转化率和对映体过量值有显著的影响.环糊精是通过提高酵母液的催化效率和对底物形成包结来影响反应结果的,其中底物芳环对位有无取代基是添加剂影响反应结果的关键因素.环糊精加入量根据底物的不同在3~20mmol/L之间较合适.     

α-咪唑苯乙酮的超声波合成

在无水乙醚中以溴和苯乙酮为原料合成了α-溴代苯乙酮;在超声作用下,α-溴代苯乙酮再与咪唑反应生成α-咪唑苯乙酮,其结构经IR,^1H NMR和MS表征。     

使用DBDMH和Et3N·3HF的苯乙酮一锅法α-亲核氟代

报道一种通过溴代和氟代的一锅法操作,从苯乙酮直接制备α-氟代苯乙酮的新方法.使用1,3-二溴-5,5-二甲基海因(DBDMH)作为溴代试剂,三乙胺三氟化氢作为氟代试剂,除了p-和m-硝基苯乙酮之外,α-氟代苯乙酮以82%～87%的收率被获得.本方法使用的试剂价廉、收率较高、操作简单方便,有较高的应用价值.     

芳香β-醛酮衍生物的合成及抗菌活性研究

鱼腥草素具有广谱的抗菌活性,其药效团为β-醛酮结构。本文以对羟基苯乙酮为原料,通过Claisen缩合、加成、缩合得到12个芳香β-醛酮衍生物,所合成化合物经过红外、核磁、质谱进行了结构表征。对所合成的化合物进行了抑菌活性测试,初步构效关系研究表明,烷氧基胺席夫碱可能是活性基团,酮羰基的存在对提高抗菌活性有利,苯环上取代基对抗菌活性有重要影响。     

蒽环与苯环间的光化学Ⅳ.烷氧基取代基与光化学反应

蒽的光化学反应在很多领域有广泛的应用,如超分子体系的标记剂,敏化剂,分子荧光传感器等,使蒽的光化学-直成为最重要的光化学反应之一[1-3].我们在近年发现3,5-二烷氧基苯基蒽衍生物可以发生蒽环与苯环间的光致可逆环加成反应,反应是定量进行的,这种光致可逆反应性能可以用作分子光开关器件,在材料科学中有着重要的应用前景[4];进一步的研究结果表明,苯环上的取代基对蒽环与苯环间的光致环加成反应有重要的影响.2,5-烷氧基双取代蒽环衍生物、3,5-二烷氧基双取代、3,4,5-三烷氧基取代时,都可以发生蒽环与苯环间的光致环加成反应;但是,苯环上4-单取代、2,3-双取代时,不能发生蒽环与苯环间的光致环加成反应,只能发生蒽环与蒽环间的光致环加成反应;苯环上3-烷氧基单取代时,可发生两种光致环加成反应.蒽环与苯环间的光致环加成反应产物(烯醇醚)在微量酸催化下发生裂解,产生单降解产物(单环酮)和双降解产物(双环酮),蒽环与蒽环间的光致环加成反应产物不能被酸催化下发生裂解,因而得不到单酮和双酮产物.     

对硝基苯乙酮的合成

從乙醯苯胺、醋酸酐與氯化鋅作用,經水解後製得對胺基苯乙酮。在氟硼酸水溶液中重氮化之,再在亞硝酸鈉的水溶液中以銅粉為觸媒,將此重氮團置換成爲硝基,即得對硝基苯乙酮。     

Metastable decay and binding energies of van der Waals cluster ions

In this work the appearance potentials for the metastable decay channel of a series of van der Waals dimer ions are presented. Ionization and metastable dissociation is achieved by resonance-enhanced two-photon absorption in a linear reflection time-of-flight mass spectrometer. From the appearance potentials the binding energy of the neutral dimers is obtained and from the additionally measured ionization potentials binding energies of the dimer cations are achieved. The contribution of charge transfer resonance interaction to the binding in cluster ions is evaluated by investigation of several homo-and heterodimers of aromatic components and the heterodimer benzene/cyclohexane as an example for a dimer consisting of an aromatic and a nonaromatic component.     

Fused Corrole Dimers Interconvert between Nonaromatic and Aromatic States through Two‐Electron Redox Reactions

A singly linked corrole dimer was synthesized by condensation of a dipyrromethane‐1‐carbinol with 1,1,2,2‐tetrapyrroethane. Oxidation of the dimer gave doubly linked corrole dimers 9 and 10 as the first examples of fused corrole dimers involving a meso–meso linkage. Dimers 9 and 10 exhibit characteristic ¹H NMR spectra, absorption spectra, excited‐state dynamics, and two‐photon absorption (TPA) values, which indicate the nonaromatic nature of 9 and the aromatic nature of 10 . Interestingly, 9 is fairly stable despite its unusual 2H‐corrole structure, which has been ascribed to the presence of two direct connections between the individual corrole units.     

Borane-mediated aldol cycloreduction of monoenone monoketones: diastereoselective formation of quaternary centers

Exposure of monoenone monoketones to catecholborane in THF at ambient temperature results in tandem 1,4-reduction-aldol cyclization. For aromatic and heteroaromatic enones, six-membered cyclic aldol products are formed in excellent yield with high levels of syn diastereoselectivity. Five-membered ring formation proceeds less readily, but the yield of cyclized product is improved through introduction of Rh(I) salts.     

Aromaticity on the pancake-bonded dimer of neutral phenalenyl radical as studied by MS and NMR spectroscopies and NICS analysis

We have demonstrated the first MS and NMR observation of a face-to-face pi-bonded dimer of an organic radical (pancake-bonded dimer coined by R. S. Mulliken) in solution, using tri-tert-butylated phenalenyl radical 1, a 3-fold symmetric neutral hydrocarbon. In addition to the direct detection of the dimer signal by cold-spray ionization mass spectrometry (CSI-MS), 1H and 13C NMR spectra in solution gave definitive evidence of a well-defined D3d dimer structure with a 12-center-2-electron-long C-C bond formation, which is the same symmetry as seen in the crystalline state. On the basis of the NMR peaks of the dimer in the aromatic region (6.47 ppm for 1H NMR and 120-143 ppm for 13C NMR), we carried out nucleus-independent chemical shift (NICS) analysis, which showed that the ring center of the dimer became more aromatic (-7.1 ppm) than that of the monomer (-3.8 ppm). The trend of aromaticity generation was more pronounced in the interior of the dimer, which has been interpreted by the negative electron density induced in the bonding region as seen in the electrostatic potential surface.     

Nitrile ylide dimerization: investigation of the carbene reactivity of nitrile ylides

A series of novel hexaaryl diazatrienes 5 ("nitrile ylide dimers") were synthesized directly from the corresponding diaryl ketimines 12 and dichlorotoluenes 13 in a facile one-pot synthesis. The carbene character of the nitrile ylides was investigated by varying the substituents on the aromatic ring adjacent to the carbene center. The isolation of the corresponding carbene dimers as stable crystalline materials with absorption maxima (lambda(max)) from 363 to 422 nm was shown to be promoted by the absence of strongly electron-withdrawing substituents. The crystal structures indicate that the E-isomers were isolated when phenyl, 3-methylphenyl, and 3-chlorophenyl substituents are present at the carbene carbon; the Z-isomer was isolated when the more sterically hindered 2,4,6-trimethylphenyl substituent (Mes) is present. The (1)H NMR spectra of the E-isomers demonstrate the nonequivalence of the aromatic rings, in which two of the aromatic rings of the imine moiety are pseudoaxial and the remaining aromatic rings are pseudoequatorial. The reactions proceed via the intermediate nitrile ylides 1 generated by the base-promoted 1,1-elimination of HCl from the intermediate chloroimine 14. The nitrile ylide was also generated by 1,3-elimination of HCl from the imidoyl chloride 18, confirming common pathways via the nitrile ylide as the dimer products obtained from these different routes were identical. The strongly electron-withdrawing 4-nitrophenyl substituent promotes the linear carbanion character of the 1,3-dipole and no dimer is formed.     

β-Keto ester aminolysis of pheophorbide a methyl ester: a facile route for asymmetric chlorin ring substitution

A chemoselective aminolysis of the β-keto ester of pheophorbide a methyl ester is demonstrated opening a facile access to an asymmetric amide functionalization of a chlorin ring using a range of aromatic and aliphatic, primary and secondary amine nucleophiles. Aminolysis of pheophorbide a methyl ester with trans-1,2-diaminocyclohexane is shown to give a symmetric open face chlorin dimer.     

Minimalist protein design: a beta-hairpin peptide that binds ssDNA

A 28-residue beta-hairpin dimer (WKWK)2 with two Trp and two Lys residues on one face of each beta-sheet was shown to form a complex with single-stranded oligonucleotides at low micromolar concentrations. Each beta-hairpin of the dimer contains a cross-strand Trp-Trp pair in a diagonal orientation which has previously been shown to create a cleft for the intercalation of aromatic guests such as adenine (J. Am. Chem. Soc. 2003, 125, 9580). The beta-hairpin dimer binds 5-residue ssDNA sequences 5'-AAAAA-3', 5'-TTTTT-3', and 5'-CCCCC-3' in water with dissociation constants in the range of 12-30 muM. A weak energetic preference for binding to sequence 5'-AAAAA-3' was observed, which is believed to result from stronger stacking interactions between Trp and the adenine base. The interaction of 5'-AAAAA-3' with the Lys and Trp residues of the peptide was evident by NMR, and a 1:1 association was demonstrated. The recognition of an 11-residue ssDNA sequence occurred with a dissociation constant of 3 muM under near-physiological ionic strength and pH, demonstrating that the beta-hairpin dimer binds ssDNA as strongly as many naturally occurring proteins. The salt dependence of the interaction of the 11-residue oligonucleotide with the peptide dimer indicates that Trp-nucleobase stacking interactions contribute about -4 kcal/mol to recognition, which is much greater than the contribution of nonionic interactions in unstructured peptides containing Trp. Moreover, recognition of the ssDNA demonstrated reduced salt dependence relative to the corresponding duplex, resulting in selectivity for ssDNA under high salt conditions. Peptide (WKWK)2 is a relevant mimic of OB-fold (oligonucleotide/oligosaccharide-binding) proteins which bind ssDNA on the surface of a beta-sheet.     

Synthesis of pyridinium salts by the reaction of α, β-unsaturated ketones,primary amines,and compounds with labile hydrogen atoms

The reaction of , -unsaturated ketones or Mannich bases of ketones with primary aromatic amines and ketones (monoketones or dimedone) in the presence of polyhalo-alkanes leads to pyridinium, 5,6,7,8-tetrahydroquinolinium, or sym-octahydroacridinium salts. The reaction of benxalcyclohexanone with primary aromatic amines and malonodinitrile makes it possible to obtain 2-amino-3-cyano-5,6,7,8-tetrahydroquinolinium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1060–1064, August, 1985.     

Ab initio quantum chemical investigation of the ground and excited states of salicylic acid dimer

The structure and stability of different forms of salicylic acid dimer have been examined by Hartree-Fock and density functional theoretic calculations using 6-31G(d,p) and 6-311++g(d,p) basis sets. Vertical excitation energies for the monomer as well as the dimer have been computed using the time-dependent density functional theory using 6-311++G(d,p) basis set. The predicted absorption maxima for the first excited singlet state of salicylic acid monomer and the dimer of the primary form are in reasonable agreement with the experimental result. There is a slight red shift (approximately 6 nm) in the absorption maximum in going from the monomer to the dimer, in accord with the experimental observation. Configuration-interaction calculations including single excitation have been carried out to map the potential-energy profile for the intra- as well as the intermolecular proton transfer in different forms of the dimer. The barrier for proton transfer in the ground state as well as the excited states makes it clear that most of the processes take place in the primary form and largely by intramolecular proton transfer.     

Beyond the benzene dimer: an investigation of the additivity of pi-pi interactions

The benzene dimer is the simplest prototype of pi-pi interactions and has been used to understand the fundamental physics of these interactions as they are observed in more complex systems. In biological systems, however, aromatic rings are rarely found in isolated pairs; thus, it is important to understand whether aromatic pairs remain a good model of pi-pi interactions in clusters. In this study, ab initio methods are used to compute the binding energies of several benzene trimers and tetramers, most of them in 1D stacked configurations. The two-body terms change only slightly relative to the dimer, and except for the cyclic trimer, the three- and four-body terms are negligible. This indicates that aromatic clusters do not feature any large nonadditive effects in their binding energies, and polarization effects in benzene clusters do not greatly change the binding that would be anticipated from unperturbed benzene-benzene interactions, at least for the 1D stacked systems considered. Three-body effects are larger for the cyclic trimer, but for all systems considered, the computed binding energies are within 10% of what would be estimated from benzene dimer energies at the same geometries.