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1.
Aromatic aldehydes or ketones which have electron-withdrawing groups on the benzene ring were selectively reduced to the corresponding alcohols in good yields by sodium hydrogentelluride; common aldehydes such as benzaldehyde and tolualdehyde were inert. 相似文献
2.
基于密度泛函理论的B3LYP方法, 对具有等瓣相似性的(BCO)12和(CH)12的10种异构体结构的稳定性进行了计算对比研究, 这10种异构体由三元、四元、五元和六元环组成. 环张力分析表明对羰基硼笼体系, 三元环起主要的稳定化作用, 而四元环是张力的主要来源, 对碳氢笼体系, 五元环起主要的稳定化作用. 电子差分密度表明羰基硼笼中的三元环与碳氢笼中的三元环有不同的电子结构, 导致了它们不同的张力表现. 核独立化学位移(NICS)分析表明, 尽管σ芳香性不是稳定性的决定因素, 但对笼的稳定性有一定的影响. 相似文献
3.
A. M. Nazarov S. L. Khursan G. A. Yamilova V. D. Komissarov 《Russian Chemical Bulletin》1999,48(6):1079-1085
The reactivity of 14 aldehydes with diphenylcarbonyl oxide Ph2COO was characterized by thek
33/k
31 ratio. The values ofk
33/k
31 vary from 1.3·10−2 (C6F5CHO) to 1.0 (p-Me2N-PhCHO), 70 °C, acetonitrile as the solvent. A charge transfer complex (CTC) was suggested to be primarily formed during
the reaction. The electronic effects of substituents in the reaction were analyzed using the published data. Carbonyl oxide
reacts with aldehydes as a nucleophile (at the carbon atom of the −CHO fragment to form 1,2,4-trioxolane) and also as an electrophile
(at the aromatic ring with the intermediate formation of CTC). The latter is transformed into either 1,2,4-trioxolane or the
products of oxidation of the phenyl ring.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1090–1096, June, 1999. 相似文献
4.
Jian‐Wu Zhang Yuan‐Rui Wang Jia‐Hao Pan Yi‐Heng He Wei Yu Bing Han 《Angewandte Chemie (International ed. in English)》2020,59(10):3900-3904
A deconstructive oxygenation of unstrained primary cycloalkanamines has been developed for the first time using an auto‐oxidative aromatization promoted C(sp3)?C(sp3) bond cleavage strategy. This metal‐free method involves the substitution reaction of cycloalkanamines with hydrazonyl chlorides and subsequent auto‐oxidative annulation to in situ generate pre‐aromatics, followed by N‐radical‐promoted ring‐opening and further oxygenation by 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) and m‐cholorperoxybenzoic acid (mCPBA). Consequently, a series of 1,2,4‐triazole‐containing acyclic carbonyl compounds were efficiently produced. This protocol features a one‐pot operation, mild reaction conditions, high regioselectivity and ring‐opening efficiency, broad substrate scope, and is compatible with alkaloids, osamines, and peptides, as well as steroids. 相似文献
5.
Xin Chen Qing-An Qiao Yue-Qing Jin Jie Jing Quan-Wen Liu Li-Xiang Sun Mei-Shan Wang Chuan-Lu Yang 《Journal of Molecular Structure》2009,911(1-3):70-74
A theoretical study for the water-assisted scavenging mechanism of pyridoxamine with 1,4-dicarbonyls was investigated by density functional theory (DFT) method at B3LYP/6-31G(d) basis set. Two scavenging pathways were examined: imine formation vs. pyrrole ring formation. In addition, solvent effect was performed using the Onsager model. Our calculations indicated that the pyrrole ring formation was the preferred pathway for the reaction, which results were consistent with experimental data. The participation of one water molecule in the reaction would reduce the active energy considerably and the energy barriers of all the transition states in the water-assisted reaction were much lower than those of the non-assisted reaction. The presence of a solvent in the continuum model disfavors the reaction. Hydrogen-bonding interactions and steric hindrance effect play an important role in the scavenging reaction. 相似文献
6.
Panicker CY Varghese HT Philip D Nogueira HI Castkova K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(5):1313-1320
Methyl(2-methyl-4,6-dinitrophenylsulfanyl)ethanoate was prepared by nucleophilic substitution. FT-IR and FT-Raman spectra of methyl(2-methyl-4,6-dinitrophenylsulfanyl)ethanoate were recorded and analyzed. Surface-enhanced Raman scattering (SERS) spectrum was recorded on a silver colloid. The vibrationl wavenumbers were computed by density functional theoretical (DFT) computations at the B3LYP/6-31G* level and they were found to be in good agreement with the experimental values. The molecule is adsorbed on the silver surface with the benzene ring in a 'tilted orientation'. 相似文献
7.
Charles H. Langley Jenn‐Huei Lii Norman L. Allinger 《Journal of computational chemistry》2001,22(13):1451-1475
Molecular mechanics (MM4) calculations were carried out on cycloketones for ring sizes ranging from 4 to 11 carbon atoms. The MM4 relative energies for the various conformations of the cycloketones were compared to density functional theory (DFT) calculations (B3LYP/6‐31G*), which were also carried out in this work. For small ring sizes (n=4–6), calculated molecular geometries, dipole moments, moments of inertia, and vibrational spectra were compared to experimental data. The axial–equatorial energy differences in methyl‐substituted cyclohexanones were also calculated by MM4 and compared to ab initio, DFT, and experimental results. The results of the MM4 studies on cycloketones showed significant improvement from those of MM3 calculations performed in parallel with the MM4 calculations. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1451–1475, 2001 相似文献
8.
Yuan Shi Satoshi Kojima Yohsuke Yamamoto 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):116-120
Abstract A series of Rh-PCP pincer complexes (iPrPCP)Rh(L) bearing a novel alkyl–aryl mixed “7-6-7” ring skeleton has been synthesized and fully characterized. The 7-6-7 ring skeleton in the hydrido-chloro and carbonyl species was found to assume the cis and trans conformations, respectively, in solid state as determined by single crystal X-ray diffraction analysis. This suggested a flexibility of the backbone compared with the similar but strictly fixed anthracene backbone. Electron density on the central rhodium atom was investigated by IR experiments and by DFT computations. NMR monitoring of the reaction of the hydrido-chloro complex with base followed by application of H2 showed the presence of what are likely to be the active 14e? species and the dihydride derivative. Especially, noteworthy is the former that was found to be relatively stable, in contrast to the corresponding iridium complex. [Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon for the following free supplemental files: Additional text, tables, and figures.] 相似文献
9.
An environmentally benign [Cu(I)]-catalyzed oxidation of activated (benzylic/allylic) alcohols to the corresponding carbonyl compounds is presented. Interestingly, the reaction was also compatible with benzylic alcohols containing ortho-bromo substituents on the aromatic ring without competing with the expected intermolecular Buchwald coupling. Significantly, the catalytic system enables the synthesis of cinnamate-esters in a sequential domino one-pot fashion via oxidation followed by Wittig–Horner protocol. 相似文献
10.
11.
Calix[n]quinones, a class of cyclic oligomers composed of p‐benzoquinone structures connected by methylene, have multi‐conjugated carbonyl structures and adjustable cavities, which make their synthesis extremely attractive. In this minireview, synthetic methods of calix[n]quinones and recent synthetic experience of our group are summarized. The merits and demerits of various synthetic methods are briefly reviewed as well. When synthesizing calix[n]quinone (n≥6) with a larger ring, the reduction‐oxidation method is considered to be the most recommended. 相似文献
12.
13.
A modular approach to 5-acylated naphtho[2,1-b]benzofurans was developed where Sonogashira cross-coupling and intramolecular alkyne carbonyl metathesis were sequentially employed to build the aromatic benzene C ring of naphtho[2,1-b]benzofuran with an acyl group at the C5 position. 相似文献
14.
The detailed hydration mechanism of carbonyl sulfide (COS) in the presence of up to five water molecules has been investigated at the level of HF and MP2 with the basis set of 6-311++G(d, p). The nucleophilic addition of water molecule occurs in a concerted way across the C==S bond of COS rather than across the C==O bond. This preferential reaction mechanism could be rationalized in terms of Fukui functions for the both nucleophilic and electrophilic attacks. The activation barriers, DeltaH( not equal) (298), for the rate-determining steps of one up to five-water hydrolyses of COS across the C==S bond are 199.4, 144.4, 123.0, 115.5, and 107.9 kJ/mol in the gas phase, respectively. The most favorable hydrolysis path of COS involves a sort of eight-membered ring transition structure and other two water molecules near to the nonreactive oxygen atom but not involved in the proton transfer, suggesting that the hydrolysis of COS can be significantly mediated by the water molecule(s) and the cooperative effects of the water molecule(s) in the nonreactive region. The catalytic effect of water molecule(s) due to the alleviation of ring strain in the proton transfer process may result from the synergistic effects of rehybridization and charge reorganization from the precoordination complex to the rate-determining transition state structure induced by water molecule. The studies on the effect of temperature on the hydrolysis of COS show that the higher temperature is unfavorable for the hydrolysis of COS. PCM solvation models almost do not modify the calculated energy barriers in a significant way. 相似文献
15.
Orlova T. Yu. Nekrasov Yu. S. Petrovskii P. V. Ezernitskaya M. G. 《Russian Chemical Bulletin》2003,52(2):410-413
The reaction of 5-IC5H4(CO)2Fe-1,5-C5H4Mn(CO)3 with Me3SiCCSiMe3 (2 : 1) in the presence of Pd(MeCN)2Cl2 afforded the I(CO)2Fe(C5H4—C5H4)Mn(CO)3 complex generated through migrations of the I atom from the Cp ring to the Fe atom and of the C5H4Mn(CO)3 group from the Fe atom to the Cp ring. 相似文献
16.
将类球红杆菌 (Rhodobacter sphaeroides) 全细胞及其分离得到的羰基还原酶用于不对称催化还原多种潜手性酮类化合物, 通过比较产物的收率、ee 值、酶活力以及酶学动力学常数 Km, 探讨了类球红杆菌的催化还原性质与底物结构的关系. 结果表明, 对于类球红杆菌全细胞不对称催化还原苯乙酮衍生物, 产物 ee 值的变化遵循 Prelg 规则, 产物收率与底物苯环及侧链上取代基团的性质有关; 对于脂肪酮催化还原, 产物收率随底物链长的增加和分子量的增大而降低, 随支链数目的增加而升高, 产物 ee 值的变化也遵循 Prelg 规则. 利用羰基还原酶不对称催化还原潜手性酮类化合物发现, 对于芳香酮类化合物, 酶对 α 位为强电负性基团的底物专一性较强; 对于脂肪酮类化合物, 酶对五碳脂肪酮的专一性较高. 利用酶直接催化还原反应产物的 ee 值均为 99% 左右, 表明酶较全细胞有更高的立体选择性. 相似文献
17.
S. Stupnikova E. Petushkova D. Muceniece V. Lūsis 《Chemistry of Heterocyclic Compounds》2007,43(1):41-49
The recyclization of 1,4-dihydropyridines in aqueous-alcoholic hydrochloric acid medium proceeds with cleavage of a C-N bond
and pyridine ring opening. Cyclohexenone derivatives are formed as a result of the subsequent intramolecular crotonic condensation
of the acyclic intermediate. The leaving carbonyl substituents depart simultaneously with recyclization, depending on the
acidity of the reaction medium.
Dedicated to Prof. Dr. E. Lukevics on the occasion of his 70th birthday.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 49–58, January, 2007. 相似文献
18.
The kinetics of Tl(III) acetate oxidation of semicarbazones of benzaldehyde and substituted benzaldehydes have been investigated
in aqueous (90%) acetic acid. Electron-releasing substituents in the phenyl ring enhance the rate of the reaction, whereas
electron-withdrawing substituents retard the rate. The rho value of −1 favours electron-deficient transition state. To account
for the major product of the reaction,viz respective benzaldehyde, a suitable scheme involving N-thallated intermediate has been proposed 相似文献
19.
Marco J. van der Burgt Jouke Jansen A.Herbert Huizer Cyril A.G.O. Varma 《Journal of Molecular Structure》1996,385(3):175-183
The X-ray diffraction of crystalline 1,2-dihydro-3H-benz[e]inden-3-one (DHBI) reveals that the molecular geometry is fully planar in the electronic ground state. Glassy solutions of naphthaldehyde, 2-acetonaphthone and methyl 2-naphthoate in the mixtures methylcyclohexane/iso-pentane (MIP) and methanol/ethanol (ME) are phosphorescent. DHBI in ME shows phosphorescence, but in MIP it is non-phosphorescent. The phosphorescence spectra of these compounds and of naphthalene have a strong resemblance. This is in accordance with a molecular distortion in the lowest triplet state, which decouples the π electron systems of the carbonyl group and the naphthyl group. The absence of phosphorescence of DHBI in MIP, indicates a geometry of the triplet state, having a non-planar naphthalene ring, when the molecule is in the non-hydrogen bonded form. 相似文献
20.
A series of polymer-supported RCpCpTiCl2 (Cp = η5 C5H5; RCp=η5 RC5H4) has been prepared and reduced by i-C3H7MgBr in situ, then used as catalysts in hydrogenation of styrene, isomerization of 1,5-cyclooctadiene and 1,5-hexadiene, and reduction of carbonyl compounds. In some cases, the introduction of a polymer ligand on the Cp ring restricts the aggregation of active sites and the formation of the inactive dimer of the titanocene species, and results in an increase of activity. Regeneration of polymer-supported titanocene catalysts was performed and the results are presented and briefly discussed. 相似文献