共查询到20条相似文献,搜索用时 9 毫秒
1.
Hatzimarinaki M Roubelakis MM Orfanopoulos M 《Journal of the American Chemical Society》2005,127(41):14182-14183
The photocycloaddition of vinylcyclopropanes to C60 yields stereospecifically a five-membered [60]fullerene adduct. These results suggest a biradical intermediate of the [2 + 2] photocycloaddition between dienes or arylalkenes and C60. An electron transfer between the triplet excited state of C60 and the unsaturated substrates precedes the formation of the intermediate. 相似文献
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《Magnetic resonance in chemistry : MRC》2002,40(6):412-414
Complete 1H and 13C NMR assignments are reported for two isomeric cyclobutanes generated from the photochemical [2 + 2] cycloaddition of N‐methylisocarbostyril and 4‐methoxy‐3‐buten‐2‐one. The reaction is 100% regioselective and demonstrates the potential synthetic utility of de Mayo type reactions using an isocarbostyril and a stable β‐dicarbonyl enol derivative. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Huda Izzat OmarYuka Odo Yasuhiro ShigemitsuTetsuro Shimo Kenichi Somekawa 《Tetrahedron》2003,59(41):8099-8105
The experimental results of the triplet [2+2] photocycloaddition reactions of substituted 2-cyclohexenone 1 with cycloalkenylesters 2, 3, 4 have showed remarkable change in the regioselectivity of the products. The ht/hh product ratio increases with increment of the cycle-size. The FMO investigations in addition to the transition state analysis were used to rationalize such regioselectivity. The FMO method with their orbital coefficients and energies could not explain the reaction selectivity since these values of 2-4 showed tendency to form the hh adduct mainly. PM3, PM5, CIS/6-31G, and B3LYP/6-31G methods were used to locate the hh and ht transition states of the three reactions. As the potential energy barriers (TS1) on the first TS surface for the major products were lower than that for the minor products in most of the cases, the real ratio can be explained in terms of TS analysis. The recently improved PM5 and the B3LYP methods were more successful in this debate as partitioning the activation energy at the potential energy barriers into reactant deformation and the interaction (or repulsion) energies is easy and effective. The changes in the ht/hh ratio with the enlargement of the alkene ring size may be due to the increment of the repulsion energy and large changes in the deformation energy of the reactants. In the transition state structures the stabilities of the major products are thought to be due to the existence of some repulsion between the enone carbonyl and esters in the alkenylesters, and some hydrogen bonding between the reactants. The FMO and second transition state (TS2) energy on the biradical intermediates are also thought to play some role in controlling the product selectivity by lowering the closure energy of the biradicals according to the possibility of their overlapping. 相似文献
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Pyrrolidinofullerenes were synthesized by reaction of C60 fullerene with N-methylglycine and substituted aromatic aldehydes.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1695–1697.Original Russian Text Copyright © 2004 by Loginova, Gunkin.This revised version was published online in April 2005 with a corrected cover date. 相似文献
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Macabeo AP Gehle D Krohn K Franzblau SG Aguinaldo AM 《Natural product communications》2012,7(6):743-745
A synthesis of a new alkaloid-fullerene conjugate (1) is reported. The reaction was carried out by photoinduced [3+2] cycloaddition of the Alstonia indole alkaloid, 6,7-seco-angustilobine B (2), to fullerene[C60] (3) under aerobic conditions. The major monoaddition photoadduct (1) was characterized unambiguously by UV, IR, MALDI-TOFMS and NMR experiments. A mechanism highlighted by sequential photoinduced electron transfer andradical recombination pathways is also proposed. No significant enhancement in inhibition against M. tuberculosis H37Rv was observed for 1 compared with its parent compounds 2 and 3. 相似文献
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The double [3 + 2] photocycloaddition reaction involving arenyl-dienes has been used to assemble seven separate [5.5.5.5] fenestrane structures that include ether and aza variants. The primary photolysis step was a meta photocycloaddition reaction, while a secondary photocycloaddition step formed the fenestrane structure. Investigations involving the insertion of an additional methylene group into the basic arenyl-diene skeleton failed to afford the desired [5.5.5.6] fenestrane structure. The presence of an oxime moiety in the aromatic photosubstrate allowed the primary photolysis step to take place; however, an attempted secondary photocycloaddition reaction involving the oxime did not provide the intended polyheterocyclic fenestrane. An alternative strategy to form various "criss-cross" double meta photocycloadducts was investigated and led to the discovery of a Paterno-Büchi cycloaddition reaction between acetone and an angular meta photocycloadduct. Other novel thermally and photochemically mediated skeletal rearrangement reactions were also recorded. 相似文献
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Evidence is presented to support the conclusion that the [2+2] photocycloaddition of acrylonitrile to naphthalene has a late transition state similar in volume to those in concerted thermal cycloadditions. 相似文献
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The functionalisation of C60 fullerene with 2,3-dimethylene-1,4-dioxane (I) and 2,5-dioxabicyclo [4.2.0]octa-1(8),6-diene (II) was investigated by the use of density functional theory calculations in terms of its energetic, structural, field emission, and electronic properties. The functionalisation of C60 with I was previously reported experimentally. The I and II molecules are preferentially attached to a C—C bond shared and located between two hexagons of C60 via [4+2] and [2+2] cycloadditions bearing reaction energies of ?15.9 kcal mol?1 and ?72.4 kcal mol?1, respectively. The HOMO-LUMO energy gap and work function of C60 are significantly reduced following completion of the reactions. The field electron emission current of the C60 surface will increase after functionalisation of either the I or II molecule. 相似文献
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Irradiation of an azo-propellane derivative in which an olefinic bond is proximate to the azo group forms a cage compound containing a 1,2-diazacyclobutane ring. 相似文献
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Intramolecular photocycloaddition (>290 nm) between a 1,3-enyne and a 2-pyridone is far more selective than the intermolecular version; a three-atom linkage both controls regiochemistry and separates the [2 + 2] and [4 + 4] pathways. All four head-to-head, head-to-tail, tail-to-head, and tail-to-tail tetherings have been investigated. Linkage via the ene of the enyne leads to [2 + 2] products regardless of alkene geometry, whereas linkage through the yne results in [4 + 4] cycloadducts. The bridged 1,2,5-cyclooctatriene products of [4 + 4] cycloaddition are unstable and undergo a subsequent [2 + 2] dimerization reaction. 相似文献
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Sébastien Redon 《Tetrahedron letters》2006,47(5):733-736
Ring-closing metathesis of bis-O,O-alkenyl ascorbic acid derivatives affords cyclic ethers in good yields which can be further converted by irradiation at 254 nm into new polyoxacyclic structures according to a diastereoselective transannular [2+2] photocycloaddition. 相似文献
15.
Yuuki Yanagisawa Hiroki Yamaguchi Yasuhiro Nishiyama Tsumoru Morimoto Kiyomi Kakiuchi Kenji Tabata Ken Tsutsumi 《Research on Chemical Intermediates》2013,39(1):101-110
A novel chiral menthol derivative supported on silsesquioxane was easily synthesized by hydrosilylation of the corresponding arylmenthyl olefin with commercially available silsesquioxane-type hydrosilane. We evaluated the applicability of the silsesquioxane-based compound to diastereoselective [2+2] photocycloaddition reaction. The newly synthesized silsesquioxane-based chiral menthol derivative 9 indicated similar diastereoselectivity to the corresponding p-methoxyphenyl menthol derivative. 相似文献
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[STRUCTURE: SEE TEXT] The tetracyclic core of the diterpene bielschowskysin has been prepared as a single enantiomer via a stereoselective intramolecular [2+2] photocycloaddition of 5-alkylidene-2(5H)-furanone 3. 相似文献
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Teobald Kupka Michał Stachów Leszek Stobiński Jakub Kaminský 《Magnetic resonance in chemistry : MRC》2013,51(8):463-468
The 3He nuclear magnetic shieldings were calculated for single helium atom, its dimer, simple models of fullerene cages (He@Cn), and single wall carbon nanotubes. The performances of several levels of theory (HF, MP2, DFT‐VSXC, CCSD, CCSD(T), and CCSDT) were tested. Two sets of polarization‐consistent basis sets were used (pcS‐n and aug‐pcS‐n), and an estimate of 3He nuclear magnetic shieldings in the complete basis set limit using a two‐parameter fit was established. Theoretical 3He results reproduced accurately previously reported theoretical values for helium gas, dimer, and helium probe inside several fullerene cages. Excellent agreement with experimental values was achieved. 3He nuclear magnetic shieldings of single helium atom approaching various points of benzene ring were tested, and an impact of 3He confinement within fullerene cages of different size on the 3He chemical shift was determined. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
18.
Booker-Milburn KI Wood PM Dainty RF Urquhart MW White AJ Lyon HJ Charmant JP 《Organic letters》2002,4(9):1487-1489
[reaction: see text]. Irradiation of benzotriazole with a variety of maleimide derivatives leads to the stereo- and regioselective formation of aryl [2 + 2] photocycloaddition products. Further studies with 2-alkyl benzotriazole derivatives indicates that in the case of the parent benzotriazole this cycloaddition proceeds selectively via the 2H-tautomer. 相似文献
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A. R. Tuktarov A. R. Akhmetov R. F. Kamalov L. M. Khalilov M. Pudas A. G. Ibragimov U. M. Dzhemilev 《Russian Journal of Organic Chemistry》2009,45(8):1168-1174
Cyclopropanation of C60-fullerene was performed with ethyl diazoacetate in the presence of Pd(PPh3)4 catalyst. A probable reaction mechanism is suggested. 相似文献
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Tuktarov A. R. Akhmetov A. R. Sabirov D. Sh. Khalilov L. M. Ibragimov A. G. Dzhemilev U. M. 《Russian Chemical Bulletin》2009,58(8):1724-1730
A catalytic method for the efficient synthesis of 5,6-open and 6,6-closed (2π+1π) fullerene adducts by [2+1] cycloaddition
of ethyl 2-alkyl(hetaryl)-2-diazoacetates to [60]fullerene in the presence of a three-component catalyst Pd(acac)2—PPh3—Et3Al have been developed. 相似文献