Comparative electron impact mass spectra of new 5-benzylidene-4,5-dihydro-(2H)-pyridazin-3-ones and 4-benzylidene-4,5-dihydrooxazin-6-ones

Electron impact mass spectra are reported for a series of 5-benzylidene-4,5-dihydro-(2H)-pyridazin-3-ones and 4-benzylidene-4,5-dihydrooxazin-6-ones.     

Synthesis and electron impact mass spectra of 3-substituted 2-acylaminoindazoles

3-Substituted-2-acylaminoindazoles 2 were prepared via oxidative cyclization of o-aminoaryl ketone acylhydrazones 1 with iodosobenzene diacetate. Their electron ionization mass spectra were recorded and in addition to the molecular ions show common fragmentation pathways corresponding to the [M-N₂]⁺, [M-NHCOX]⁺ and [M-COX]⁺ ions, with some influence on the skeletal fragmentation by different substituents.     

Synthesis of 6-substituted-4,5-dihydro-3(2H)-pyridazinones

A convenient synthetic method for the pharmaceutically important 6-substituted-4,5-dihydro-3(2H)-pyridazinones is described. The synthetic strategy is based on Δ-soxazolines chemistry which were in turn unmasked by N? O bond cleavage and cyclized to the target compounds.     

Tautomerism and electron impact mass spectra of pyrimidin-4(3H)- and -4(1H)-ones

A mass spectrometric identification and differentiation of pyrimidin-4(3H)- and -4(1H)-ones was carried out. N-Substitution at position 1 or 3 made the distinction of the two sets of compounds very easy because of their characteristic fragmentation pathways. Most interesting were the spectra of the N-unsubstituted derivatives, which illustrated a predominance of the two possible NH tautomers in relation to the 4-hydroxy structure.     

The reaction of 2-substituted-4,5-dichloro-3(2H)-pyridazinones with alkoxides and alkylthiolates

The reaction of 2-substituted-4,5-dichloro-3(2H)-pyridazinones 1a-b with alkoxides and alkylthiolates was investigated. Regiospecific displacement of either the 4 or 5 chlorine atom could be achieved in most cases by appropriate selection of the reaction solvent.     

Synthesis of isoxazolo[4,5-d]pyridazin-4(5H)-ones and 4-acyl-5-hydroxy-3(2H)-pyridazinones

The title compounds were prepared from ethyl 5-acyl- or 5-(1-hydroxyethenyl)isoxazole-4-carboxylates which in turn were prepared from ethyl 3-methylamino-2-butenoate or 3(2H)-furanones.     

The fragmentation of 5- and 3-substituted thiophene-2-carboxamides under electron impact

The 70 eV electron impact mass spectra of twelve 5- and 3-substituted thiophene-2-carboxamides are discussed with the aid of exact mass measurements and labelling experiments. All mass spectra exhibit pronounced molecular ions. Some isomeric 5- and 3-substituted title compounds can be differentiated by mass spectrometry. The fragmentation is influenced by a strong ‘ortho-effect’ which activates the NH₃ elimination. In the other cases the most important fragmentation is NH₂˙ loss, followed by CO elimination.     

6-(4-取代苯基)-5-甲基-4,5二氢-3(2H)哒嗪酮化合物的合成及其抑制血小板聚集作用

血小板聚集在血栓形成中起着先导而关键的作用,而严重威胁人类生命健康的心脑血管疾病多数与血栓形成和血栓栓塞有着密切的联系[1]。二氢哒嗪酮类化合物对抑制血小板聚集有较强的药理活性,对二磷酸腺苷(ADP)、花生四烯酸(AA)、血小板活化因子(PAF)和胶原(Collagen)引起的血小板聚集均有抑制作用。深入研究二氢哒嗪酮类化合物的构效关系,以期寻找活性更强的抗血小板聚集药物,是开发新型心脑血管系统疾病药物的重要研究方向之一。本文设计合成了6-(4-取代苯基)-5-甲基-4,5二氢-3(2H)哒嗪酮类化合物[2,3,4],并进行了体外药理实验。1实验部…     

5-α-(磷酸基)苄基-2-甲基-4-羟基咪唑衍生物的电子轰击质谱研究

本文报道了六种新的咪唑衍生物的电子轰击质谱,着重讨论了P--C, P--N键的断裂; 产物离子的开环反应;产物离子的H重排反应和失去CO的反应等. 根据高分辨精确质量测量和联动扫描技术, 讨论了化合物的质谱裂解机理.     

Electron impact mass spectra of 1-methyl-3-(2-benzothiazolylhydrazono)-2-indolinones

A study of the fragmentation of l-methyl-3-(2-benzothiazolylhydrazono)-2-indolinones on electron impact reveals that the major processes involve N? N bond fission and the competing loss of CO from the molecular ion.     

Mass spectra of 3(2H)-cinnolinone and 2-substituted derivatives

The mass spectrum of 3(2H)-cinnolinone indicates that it undergoes fragmentation in a fashion similar to other heterocyclic systems containing two vicinal nitrogens. The initial fragmentation, loss of CO, gives a 1H-indazole radical cation, as was shown by deuterium labelling and metastable ion spectra. Four 2-substituted-3(2H)-cinnolinones were also studied and it was found that their fragmentation patterns are highly influenced by the substituent groups.     

Studies in organic mass spectrometry. IV. Electron impact induced fragmentation of 2-substituted 3-(5-isoxazolyl)-4(3H)-quinazolinones of pharmaceutical interest

The fragmentation under electron impact of thirteen 2-substituted-3-(5-isoxazolyl)-4(3H)-quinazolinones has been investigated with the aid of metastable ion detection and high resolution measurements. Molecular ions are always abundant and the main primary fragmentation route involves acetonitrile elimination through isoxazole ring opening. The other common processes, particularly those leading to the abundant [R-C₈H₄N₂]⁺ ion ( b or b' ), as well as those due to the nature of the 2-substituent are reported and discussed.     

Facile synthesis of 4,5-disubstituted-3(2H)-pyridazinones

4,5-Disubstituted-3(2H)-pyridazinones were initially synthesized via sodium alkoxide additions to an advanced bromide intermediate. A small parallel chemistry effort resulted in a poor success rate, and we thus increased the reactivity of the reaction partner by performing a copper-catalyzed Finkelstein reaction. Copper-catalyzed coupling of a diverse set of alcohols with the resulting iodide resulted in a more successful effort. A number of alternative syntheses of this series of compounds are also described and these methods proved to be versatile, efficient, and amenable to parallel synthesis.     

The mass spectra of 3-substituted furans

A fragmentation pattern characteristic of 3-substituted furans, in which the 3-substituent carries an oxygen function, is discussed. Examination of the spectra of some meliacins, as well as those of some synthetic model compounds, illustrates the diagnostic value of this particular fragmentation. In addition the spectrum of methyl limonilate (III, R = CH₃) is discussed in some detail.     

Electron impact mass spectra of new 5-substituted-2-amino-2-oxazolines

The electron impact mass spectra of fifteen 5-substituted-2-amino-2-oxazolines classified in two series according to the nature of the substituent are discussed. For the 5-(l-aryl-4-piperazino)methyl compounds the main fragments are derived from the arylpiperazine moiety, whereas for the phenoxymethyl compounds the main ions are derived from the heterocyclic oxazoline ring.     

Novel 5,6-bis-(4-substitutedphenyl)-2H(3)-pyridazinones: Synthesis and reactions

A series of 5,6-bis(4-substitutedphenyl)-2H(3)-pyridazinones 2a–f have been synthesized from the condensation of the corresponding benzil monohydrazones 1 either with ethyl cyanoacetate or diethyl malonate in ethanol. The synthesized pyridazinones were converted to the corresponding 3-chloro derivatives 3a–f by the action of phosphoryl chloride. Reaction of the latter halogenated pyridazines with various aromatic amines led to the formation of new 3-aminoaryl pyridazines (4) in moderate yield. The structures of all new compounds 2b,c,e,f, 3b–e, 4 were fully identified by the analysis of their ¹H and ¹³C NMR and mass spectra. Some of these synthetic heterocyclic compounds were screened for their antimicrobial activities but they were almost negative.