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11.
12.
Gianni Podda Luciana Corda Carlo Anchisi Beatrice Pelli Pietro Traldi 《Journal of mass spectrometry : JMS》1987,22(3):162-168
Electron impact mass spectrometry has been used together with linked scans, exact mass measurements and mass-analysed ion kinetic energy spectrometry to study nine inacrocyclic polyether lactones in detail. The presence of abundant hydrogenated oxirane ions has been observed for all the compounds examined, and confirmed by kinetic energy release measurements. 相似文献
13.
Carlo Bonini Lucia Chiummiento Maria Funicello Gerardina Suanno Pietro Campaner 《Tetrahedron》2005,61(27):6580-6589
An efficient method has been developed for the synthesis of a versatile intermediate bearing azido, hydroxyl and ester functions, a useful precursor for peptidomimetic compounds. The two main features for this synthesis were the use of the Sharpless asymmetric dihydroxylation on thiophene acrylate and the subsequent regioselective ring opening by sodium azide of the cyclic sulfite. Highly chemoselective reduction of the azido alcohol led to a key compound which was utilized for the synthesis of two analogues of commercial anti HIV PR such as nelfinavir and saquinavir. The biological activity and molecular modelling study on these two new potential drugs have been evaluated. 相似文献
14.
The polar 1,4-cycloaddition of dichloroketene to N,N-disubstituted (E)-5-aminomethylene-1,5,6,7-tetrahydro-(1-methyl)(1-phenyl)-4H-indazol-4-ones V, prepared from 1,5,6,7-tetrahydro-(1-methyl)(1-phenyl)-4H-indazol-4-ones via the 5-hydroxymethylene derivatives, gave in good yield N,N-disubstituted 4-amino-3,3-dichloro-4,5,6,7-tetrahydro-(7-methyl)(7-phenyl)pyrano[2,3-e]indazol-(3H)ones VI, which are derivatives of the new heterocyclic system pyrano[2,3-e]indazole. Dehydrochlorination of VI with DBN afforded N,N-disubstituted 4-amino-3-chloro-6,7-dihydro(7-methyl)(7-phenyl)pyrano[2,3-e]indazol-2(5H]-ones VII generally in satisfactory yield. Full aromatization with DDQ of VII was tried only in the case of dimethylamino derivatives, giving a moderate yield of 3-chloro-4-dimethylamino(7-methyl)(7-phenyl)pyrano[2,3-e]indazol-2(7H)-ones. Cycloaddition of sulfene to V occurred only in the case of aliphatic N-substitution to give in moderate yield 4-dialkylamino-4,5,6,7-tetrahydro-(7-methyl)(7-phenyl)-3H-1,2-oxathiino[6,5-e]indazole 2,2-dioxides, which are derivatives of the new heterocyclic system 1,2-oxathiino[6,5-e]indazole. 相似文献
15.
The radiolysis of β(−)pinene has been studied at five different radiation dose, namely at 50, 100, 150, 300 and 600 kGy with
a dose rate of 2.2 kGy/h. At lower radiation dose, β(−)pinene showed a reduction of the optical activity, hence, the expected
radioracemization appeared predominant. At higher radiation dose, an opposite and unexpected trend was observed: the optical
activity increased almost linearly with the radiation dose. The increase of [α]D of radiolyzed β(−)pinene was due to the formation oligomers, mainly a dimer and/or a trimer of β(−)pinene which remain soluble
in the monomer but which displayed a higher optical activity than the starting monomer, contributing to the increase in the
specific optical rotation. Simultaneously to the formation of the dimer/trimer the radiolysis of β(−)pinene induced also its
polymerization into a poly(β(−)pinene) resin which was insoluble in the monomer and which was characterized by a high structural
order and by the preservation of the chiral centers so that it showed an enhanced specific optical rotation which is ≈2 times
that of the monomer. It is shown that poly(β(−)pinene) radiopolymer can be easily racemized in presence of a Friedel-Crafts
catalyst. The kinetics of β(−)pinene radiation-induced oligomerization and polymerization can be described by a pseudofirst
order rate constant k = 1.9·10−7·s−1. The radiation chemical yield for the same reaction is G = 1.93·10−6 mol/J. The work shows that also the radiation-induced polymerization of chiral monomers may be a tool for the preservation
and amplification of the optical activity of the monomer with implications for abiotic mechanisms of chiral amplification. 相似文献
16.
Alberto Ballistreri Domenico Garozzo Mario Giuffrida Pietro Maravigna Giorgio Montaudo 《Journal of polymer science. Part A, Polymer chemistry》1986,24(2):331-346
The thermal fragmentation processes in poly-Schiff bases have been investigated by direct pyrolysis–mass spectrometry. The mass spectral data show that the thermal fragmentation occurring in the polymers under investigation is characterized by hydrogen transfer reactions. In the case of a totally aromatic poly-Schiff base (polymer I ), the thermal fragmentation process involves hydrogen transfer irom the methyne group with formation of fragments bearing nitrile and/or phenyl end groups. In the case of aromatic-aliphatic poly-Schiff bases (polymers II–IV ), the hydrogen transfer process occurs from the aliphatic methylene groups. The latter process involves a lower energy and therefore occurs at lower temperatures with respect to the totally aromatic polymer I , with formation of thermal fragments bearing olefin and/or imine end groups. Beside these fragments, several thermal fragmentation compounds are also evolved by multiple hydrogen transfer reactions. 相似文献
17.
Pietro Borgna Massimo Pregnolato Anna Gamba Invernizzi Giorgio Mellerio 《Journal of heterocyclic chemistry》1993,30(4):1079-1084
3H-1,2-Dithiolo[3,4-b]pyridine-3-thione ( 10 ) reacts with primary alkylamines to give 1,2-dihydro-2-thioxo-3-pyridinecarbothioamides 11a-g and two minor products. Isothiazolo[5,4-b]pyridine-3(2H)-thiones 12a-g and 3-imino-3H-1,2-dithiolo[3,4-b]pyridines 13a-g were isolated and characterized. Further investigations allowed the synthesis of 12 and 13 in good yield. 相似文献
18.
Dimethylcarbonate (DMC) is a valuable methylating reagent that can replace methyl halides and dimethylsulfate in the methylation of a variety of nucleophiles. It couples tunable reactivity and unprecedented selectivity towards mono-C- and mono-N-methylation. In addition, it is a prototype example of a green reagent, because it is nontoxic, is made by a clean process, is biodegradable, and reacts in the presence of a catalytic amount of base, thereby avoiding the formation of undesirable inorganic salts as by-products. Depending on the reaction conditions, DMC can be reacted under plug-flow, CSTR, or batch conditions. Other remarkable reactions are those where DMC behaves as an oxidant. The reactivity of other carbonates is reported as well. 相似文献
19.
Antonio Selva Pietro Traldi Luigi F. Zerilli Gian Gualberto Gallo 《Journal of mass spectrometry : JMS》1976,11(2):217-218
The retro 1,3-dipolar cycloaddition induced by electron impact on 3,5-diphenyl-1,2,4-oxadiazole is interpreted as a two-step process on the basis of the energetics and kinetics of the fragments [C7H5NO]+., [C6H5CN]+. and [C6H5CO]+. 相似文献
20.
W. Daniel Carlisle David E. Fenton Patrick B. Roberts Umberto Casellato Pietro A. Vigato Rodolfo Graziani 《Transition Metal Chemistry》1986,11(8):292-295
Summary The crystal structure of the dinuclear complex [Cu2(C26H30-N4O2)(H2O)2](BF4)2 was determined by x-ray crystallography. The crystals are triclinic, P¯1, witha = 10.945(5),b = 8.703(5),c = 8.495(5) Å, = 103.86(3)°, = 105.73(3)°, = 85.77(3)°, V = 756 Å3 Dc = 1.65 g cm–3 for Z = 1. The copper(II) atoms are 5-coordinate and square-pyramidal. Selected bond distances are: Cu-N, 1.91 Å (mean); Cu-O(base) = 1.90(1) and 1.91(1) Å; Cu-O(apical) = 2.47(1) Å; There are O(water)-H ... F interionic hydrogen bonds in the structure. The Cu .. Cu distance is 2.847 Å. 相似文献