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1.
The enynyl‐substituted 2,3‐dihydroisoxazoles (‘isoxazolines') 9 – 14 were prepared by highly (Z)‐selective Peterson olefination reaction from the corresponding carbaldehydes 6 – 8 . On short‐time thermolysis (280 – 406°/10 s) the TMS derivatives 9 – 11 give rise to the annulated pyrrolines 18 – 20 , which, in some cases, suffer CH4 elimination affording the pyrroles 15 – 17 . In contrast, thermolysis of the terminal alkyne derivatives 12 – 14 leads to the bicyclic compounds 21 – 23 . The reaction pathways are discussed on the basis of the formation of conjugated azomethine ylides as key intermediates, which either undergo a 1,5‐cyclization to 18 – 20 or a 1,7‐ring‐closure affording cycloallene intermediates of type V , which are further transformed into the azepino pyrroles 21 – 23 . 相似文献
2.
Three new diarylethenes 1 – 3 combined with quinoline derivatives have been synthesized. Through controlled chemical condition of deprotonation/protonation, they presented some new irreversible photochromic phenomenons under UV/Vis light irradiation in chloroform solution. It was found that 1 – 3 had well photoisomerization upon UV/Vis light irradiation in neutral chloroform solution. Addition of acid to the solution of the ring‐opening isomers of 1 – 3 produced 1oa – 3oa , which performed reversible photochromic behavior under UV/Vis light irradiation and reversed back to 1 – 3 under neutralizing with adding lewis base. However, addtion of base to neutral soluton of the ring‐opening isomers of 1 – 3 produced 1ob – 3ob , which could not change to the deprotonated ring‐closing isomers under UV light irradiation. 相似文献
3.
Optically active 2,5,6,6- and 2,4,4,5-tetraalkylcyclohex-2-en-1-ones ((+)- 2a – d and (?)- 5a – d ), important building blocks for flowery- and woody-like odorants, have been prepared. Compounds (+)- 2a – d and (?)- 5a – d were obtained by ozonolysis of the corresponding cyclopentenic precursors, followed by intramolecular aldol condensation. Alternatively, enones (+)- 2a – d were reduced to the corresponding allylic alcohols ad converted to enones (-)- 5a – d via acidic isomerization and oxidation. 13C-NMR assignments are presented. 相似文献
4.
A concise synthesis of α‐benzylidene‐γ‐methyl‐γ‐butyrolactones 5a – g from substituted benzaldehydes is described. Compounds 1a – g on reaction with phosphorane 2 , provide the pentenoates 3a – g , which can be hydrolyzed to the acids 4a – g . The latter are cyclized to the corresponding butyrolactones 5a – g in excellent yields. The pentenoates 3a – g , on acid catalyzed cyclization, also provide 5a – g in very high yields. 相似文献
5.
The syntheses of four macrocyclic spermine alkaloids, (±)‐budmunchiamine A – C ( 1a – c ) and (±)‐budmunchiamine L4 ( 1 ), were accomplished by Michael addition of spermine to the α,β‐unsaturated esters 3a – d , followed by cyclization of the resulting α,ω‐tetraamino esters 4a – d with triethoxyantimony; N‐methylation of the amino lactams 6a – c yielded the budmunchiamines A – C ( 1a – c ). 相似文献
6.
The mass spectra of aromatic hydroxylamines are diagnostic; [M], [M – 2], [M – 16] and, in most instances, [M – 17] ions are observed. 相似文献
7.
Cvetka Turk Jurij Svete Branko Stanovnik Ljubo Goli
Simona Goli
‐Grdadolnik Amalija Golobi
Lovro Seli
《Helvetica chimica acta》2001,84(1):146-156
The 5,5‐dimethylpyrazolidin‐3‐one ( 4 ), prepared from ethyl 3‐methylbut‐2‐enoate ( 3 ) and hydrazine hydrate, was treated with various substituted benzaldehydes 5a – i to give the corresponding (1Z)‐1‐(arylmethylidene)‐5,5‐dimethyl‐3‐oxopyrazolidin‐1‐ium‐2‐ide azomethine imines 6a – i . The 1,3‐dipolar cycloaddition reactions of azomethine imines 6a – h with dimethyl acetylenedicarboxylate (=dimethyl but‐2‐ynedioate; 7 ) afforded the corresponding dimethyl pyrazolo[1,2‐a]pyrazoledicarboxylates 8a – h , while by cycloaddition of 6 with methyl propiolate (=methyl prop‐2‐ynoate; 9 ), regioisomeric methyl pyrazolo[1,2‐a]pyrazolemonocarboxylates 10 and 11 were obtained. The regioselectivity of cycloadditions of azomethine imines 6a – i with methyl propiolate ( 9 ) was influenced by the substituents on the aryl residue. Thus, azomethine imines 6a – e derived from benzaldehydes 5a – e with a single substituent or without a substituent at the ortho‐positions in the aryl residue, led to mixtures of regioisomers 10a – e and 11a – e . Azomethine imines 6f – i derived from 2,6‐disubstituted benzaldehydes 5f – i gave single regioisomers 10f – i . 相似文献
8.
Tohru Yamagaki Takehiro Watanabe Masaki Tanaka Kohtaro Sugahara 《Journal of the American Society for Mass Spectrometry》2014,25(1):88-94
Negative-ion matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectra and tandem mass spectra of flavonoid mono-O-glycosides showed the irregular signals that were 1 and/or 2 Da smaller than the parent deprotonated molecules ([M – H]–) and the sugar-unit lost fragment ions ([M – Sugar – H]–). The 1 and/or 2 Da mass shifts are generated with the removing of a neutral hydrogen radical (H*), and/or with the homolytic cleavage of the glycosidic bond, such as [M – H* – H]–, [M – Sugar – H* – H]–, and [M – Sugar – 2H* – H]–. It was revealed that the hydrogen radical removes from the phenolic hydroxy groups on the flavonoids, not from the sugar moiety, because the flavonoid backbones themselves absorb the laser. The glycosyl positions depend on the extent of the hydrogen radical removals and that of the homolytic cleavage of the glycosidic bonds. Flavonoid mono-glycoside isomers were distinguished according to their TOF MS and tandem mass spectra. Figure
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9.
《Progress in Surface Science》2007,82(2-3):55-120
Metal oxides are virtually everywhere – only gold has the property not to form an oxide on its surface when exposed to the ambient. As a result, understanding the physics and chemistry of oxide surfaces is a topic of pronounced general interest and, of course, also a necessary prerequisite for many technical applications. The most important of these is certainly heterogeneous catalysis, but one has to realize that – under ambient conditions – virtually all phenomena occurring at liquid/metal and gas/metal interfaces are determined by the corresponding oxide. This applies in particular to friction phenomena, adhesion and corrosion. A necessary – but not necessarily sufficient – condition for unravelling the fundamentals governing this complex field is to analyze in some detail elementary chemical and physical processes at oxide surfaces. Although the Surface Science of metal surfaces has seen a major progress in the past decades, for oxides detailed experimental investigations for well-defined single crystal surfaces still represent a formidable challenge – mostly because of technical difficulties (charging), but to some extent also due to fundamental problems related to the stabilization of polar surfaces. As a result, the amount of information available for this class of materials is – compared to that at hand for metals – clearly not satisfactory. A particular disturbing lack of information is that about the presence of hydrogen at oxide surfaces – either as hydroxy-species or in form of metal hydrides.In the present review we will summarize recent experimental and theoretical information which has become available from single crystal studies on ZnO surfaces. While the number of papers dealing with another oxide, rutile TiO2, is significantly larger (although titania does not exhibit a polar surface), also for zinc oxide a basis of experimental and theoretical knowledge as been accumulated, which – at least for the non-polar surfaces – allows to understand physico-chemical processes on an atomic level for an increasing number of cases. In particular with regards to the interaction with hydrogen a number of – often surprising – observations have been reported recently. Some of them carry implications for the behaviour of hydrogen on oxide surfaces in general. We will present the currently available information for both, experiment and theory, and demonstrate the rather large variety of this material’s surface properties. 相似文献
10.
Zeper Abliz Junji Aoki Toyotoshi Ueda Teruo Kan Minoru Takekawa Satoshi Iwashima 《Journal of mass spectrometry : JMS》1993,28(5):607-614
Electron impact mass spectra were measured for five isomers of pyridinobenzanthrones and three isomers of benzobenzanthrones. The fragmentation pattern and intensity of M2+, [M – H]+, [M – CO]i+, [M – CO – H(or 2H)]i+ and [M – CO – HCN]i+ (i = 1, 2) ions indicated remarkable differences and very interesting features according to the isomers with or without nitrogen and condensation positions of a pyridino or benzo ring to the benzanthrone skeleton. Further, the competition of decompositions through [M – H]+, [M – CO]+˙ or [M – HCN]+˙ ions was confirmed by the observation of metastable ions and the appearance energies of fragment ions. Interesting observations from these results were expulsion of an H atom in close proximity to the area around an O?C group, a weak bonding interaction between sp2 C? H and an O?C group, inducing specific hydrogen rearrangement, and characteristic charge localization on heteroatoms. 相似文献
11.
3-Hydroxy-ceph-3-em-esters 5 a – c , versatile intermediates for the preparation of new β-lactam antibiotics, were obtained by ozonolysis of the corresponding 3-methylidene-esters 3 a – c . Reduction and elimination gave the 3-unsubstituted ester 13 ; derivatives 16 a – c and 20 – 22 resulted from O-alkylation. The 3-methoxy-esters 16 a – c were converted into the corresponding acids 23 a – d . Several other transformations of the β-ketoester system are described. 相似文献
12.
A New Route to 1, 3-Dicarbonyl Derivatives, Model Investigations on the A/B-Part of-3-Oxo-5α-steroids Starting from 1 the 1, 3-dicarbonyl compounds 4a – d were synthetized via the enynes 2a – e and the relatively unstable epoxides 3a – d . The latter were reacted with 95% formic acid to gave 4a – d ; small amounts of the furane derivatives 5a – c were identified as by-products in this last step. In the presence of catalytic amounts of HgSO4 the epoxides 3a – c yielded with 95% formic acid the furanes 5a – c , but no detectable amounts of 4a – c . 相似文献
13.
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
14.
Basak Bidyut Bandyopadhyay Debasish Banerji Avijit Banerji Julie Chatterjee Asima 《平面色谱法杂志一现代薄层色谱法》2005,18(3):251-252
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
15.
Under electron impact, 3-aryl-4-hydroxyisoquinolines form [M – H]+, [M – CO]+ and [M – H – CO]+ ions with a subsequent elimination of HCN or CH3CN. A cyclic structure for the [M – H]+ ion is suggested. The primary act of fragmentation of the corresponding methyle ether derivatives is the loss of CH3?, as well as H?; the further fragmentatio is similar to that described above. It has been established that the unusual [M – H]+, [M – OH]+ and [M – CH5?]+ ions are formed when 8 fragments. Fragmentation schemes for all compounds are proposed based upon high resolution mass spectra and deuterated analogues. 相似文献
16.
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
17.
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
18.
The glucose‐, mannose‐, and galactose‐derived spirocyclic cyclopropylammonium chlorides 1a – 1d, 2a – 2d and 3a – 3d were prepared as potential glycosidase inhibitors. Cyclopropanation of the diazirine 5 with ethyl acrylate led in 71% yield to a 4 : 5 : 1 : 20 mixture of the ethyl cyclopropanecarboxylates 7a – 7d , while the Cu‐catalysed cycloaddition of ethyl diazoacetate to the exo‐glycal 6 afforded 7a – 7d (6 : 2 : 5 : 3) in 93–98% yield (Scheme 1). Saponification, Curtius degradation, and subsequent addition of BnOH or t‐BuOH led in 60–80% overall yield to the Z‐ or Boc‐carbamates 11a – 11d and 12a – 12d , respectively. Hydrogenolysis of 11a – 11d afforded 1a – 1d , while 12a – 12d was debenzylated to 13a – 13d prior to acidic cleavage of the N‐Boc group. The manno‐ and galacto‐isomers 2a – 2d and 3a – 3d , respectively, were similarly obtained in comparable yields (Schemes 2 and 4). Also prepared were the differentially protected manno‐configured esters 24a – 24d ; they are intermediates for the synthesis of analogous N‐acetylglucosamine‐derived cyclopropanes (Scheme 3). The cyclopropylammonium chlorides 1a – 1d, 2a – 2d and 3a – 3d are very weak inhibitors of several glycosidases (Tables 1 and 2). Traces of Pd compounds, however, generated upon catalytic debenzylation, proved to be strong inhibitors. PdCl is, indeed, a reversible, micromolar inhibitor for the β‐glucosidases from C. saccharolyticum and sweet almonds (non‐competitive), the β‐galactosidases from bovine liver and from E. coli (both non‐competitive), the α‐galactosidase from Aspergillus niger (competitive), and an irreversible inhibitor of the α‐glucosidase from yeast and the α‐galactosidase from coffee beans. The cyclopropylamines derived from 1a – 1d or 3a – 3d significantly enhance the inhibition of the β‐glucosidase from C. saccharolyticum by PdCl , lowering the Ki value from 40 μM (PdCl ) to 0.5 μM for a 1 : 1 mixture of PdCl and 1d . A similar effect is shown by cyclopropylamine, but not by several other amines. 相似文献
19.
[2+2] macrocyclic Schiff bases of three kinds have been synthesized from chiral 1,4-diamines by use of different methods. Macrocyclic Schiff bases 1a-1c have been selectively obtained based on a non-templated dilution method from chiral 1,4-diamines a-c and dialdehyde DA1, whereas macrocycles 2a-2c have been selectively produced from reaction of diamines a-c and dialdehyde DA2 in the presence of boric acid as templates. Macrocyclic Schiff bases 3a-3c have been afforded in high selectivity from diamines a-c and dialdehyde DA3 by means of sodium-template. All the titled compounds have been confirmed by ^1H NMR and ESI-MS analyses. 相似文献
20.
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献