1,4-氧氮杂萘-2-酮类衍生物的电子轰击质谱分析

用电子轰击质谱(EI-MS)研究了1,4-氧氮杂萘-2-酮系列衍生物,分析并探讨了不同取代基对这类化合物EI-MS谱图的影响,分析得到一些裂解规律。     

Structural Effects in the Addition–Fragmentation Reaction of Allylic Onium Salts

Allylic onium salts with different hetero‐atoms and various substituent groups at the allylic double bond have been shown to be very efficient initiators for cationic polymerization. When attacked by a radical, they become radical cations, which are highly unstable species, and undergo fragmentation into smaller radical cations called onium radical cations. The reaction mechanism involves radical formation, addition and fragmentation. In our previous work, radical initiators generated in the same way and under the same conditions are studied experimentally for their ability to affect the polymerization efficiency. Here, the factors affecting the polymerization efficiency are discussed theoretically using semi‐empirical quantum mechanical techniques. The type of radical species, substituent group at the allylic side, the heteroatom at the onium side and the onium group itself are analyzed separately. For this purpose, the geometries of different onium radical cations to be fragmented are optimized and the strength of the C–heteroatom bond to be broken and the size of the radical cations after fragmentation are considered.     

Iodine-Catalyzed,Efficient, One-Pot Protocol for the Conversion of Araldehydes into 5-Aryl-1H-tetrazoles

An easy access to various 5-aryl-1H-tetrazoles by a one-pot direct conversion of aldehydes to tetrazoles without the isolation of the intermediate nitriles using commercially available iodine as a catalyst is described. The protocol offers advantages in terms of good yields, mild reaction conditions, short reaction times, and use of readily available environmentally compatible catalyst.     

Synthesis of New Functionally Substituted 1-R-tetrazoles and Their 5-Amino Derivatives

It has been shown that amino derivatives of sulfanilamide, and also some functionally substituted primary arylamines and cycloalkylamines, undergo heterocyclization with triethyl orthoformate and sodium azide with the formation of 1-monosubstituted tetrazoles. Primary amines of the azole series, 5-aminotetrazole, 5-amino-1-methyltetrazole, 4-amino-1,2,4-triazole, and also less basic arylamines (4-fluoro-3-nitroaniline, 2,6-dibromo-4-nitroaniline) did not react. An efficient method of introducing an amino group into position C₍₅₎ of the tetrazole ring of 1-aryltetrazoles is proposed, based on alkaline decomposition of the tetrazole ring and heterocyclization of the resulting N-arylcyanamides on interaction with ammonium azide generated in situ. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1174–1179, August, 2005.     

Electron ionization mass spectral study of oxo- and thio derivatives of minor tobacco alkaloids

The electron-ionization mass spectra (EI-MS) of oxo- and thio-derivatives of minor tobacco alkaloids and structurally similar piperidine alkaloids, i.e. thiocotinine (1), 2'-oxo-N-methylanabasine (2), 2'-thio-N- methylanabasine (3), 2'-oxoanabasamine (4) and 2'-thioanabasamine (5) are discussed and general fragmentation routes of their molecular cations are proposed. Comparison of the data obtained for 1 with the EI-MS data of metameric metabolites of nicotine: 3'-hydroxycotinine, (A) and 5'-hydroxycotinine, (B) allows a differentiation between these metamers. The data will be useful for the identification of metabolites of alkaloids of these types in biological matrices.     

Ion‐Induced Fragmentation of Amino Acids: Effect of the Environment

In general, radiation‐induced fragmentation of small amino acids is governed by the cleavage of the C? C_α bond. We present results obtained with 300 keV Xe²⁰⁺ ions that allow molecules (glycine and valine) to be ionised at large distances without appreciable energy transfer. Also in the present case, the C? C_α bond turns out to be the weakest link and hence its scission is the dominant fragmentation channel. Intact ionised molecules are observed with very low intensities. When the molecules are embedded in a cluster of amino acids, a protective effect of the environment is observed. The fragmentation pattern changes: the C? C_α bond becomes more protected and stable amino acid cations are observed as fragments of the molecular clusters. Evidently, the molecular cluster acts as a “buffer” for the excess energy, capable of rapidly redistributing excess energy and charge.     

Fragmentation patterns of new esterified and unesterified aromatic 1-hydroxymethylene-1, 1-bisphosphonic acids by ESI-MSn

1-Hydroxymethylene-1,1-bisphosphonic acids (HMBPs) are compounds that have interesting pharmacological applications. Unfortunately few studies exist on their analyses by mass spectrometry (MS). In this work, we have analyzed new aromatic HMBPs and their prodrugs with electrospray tandem mass spectrometry (ESI-MS(n)). We describe, for the first time, a complete study of fragmentation patterns, in both positive and negative-ion modes. In positive mode, the cation dissociations are mainly elimination of water and phosphorus fragments. In negative mode, losses of ROH (R==H, C(6)H(5), CH(3)OC(6)H(5)) and HPO(2) were observed. The results have revealed specific structural fingerprints for the screening of these compounds in complex biological mixtures.     

Diisopropylethylammonium acetate (DIPEAc): An efficient and recyclable catalyst for the rapid synthesis of 5-substituted-1H-tetrazoles

A simple and efficient protocol developed for the synthesis of 5-substituted 1H-tetrazole derivatives through [2+3] cycloaddition reaction between benzonitriles and sodium azide using diisopropylethylammonium acetate as a recyclable reaction medium is described. The reactions proceed well at 80?°C and provide the corresponding tetrazoles in good to excellent yields (up to 94% yield). Developed method has notable advantages, such as simple and mild conditions, easy workup, reusability with consistent catalytic activity, and safer alternative to hazardous, corrosive conventional Lewis acid catalysts.     

Crystal Structure and Mass Spectrometric Fragmentation Behavior of Eprosartan

The crystal structure determination and mass spectrometric fragmentation analysis of the medicinal ingredient eprosartan （4-[2-butyl-5-（2-carboxy-3-thiophen-2-yl-propenyl）-imidazol-l-ylmethyl]-benzoic acid） are presented. The single-crystal X-ray diffraction shows that the colorless transparent crystal of eprosartan is of monoclinic system, space group P2/c with a = 16.1861（15）, b = 10.9813（12）, c = 28.610（3） A, β = 118.452（2）°, Z = 4, V= 4471.1（8） A3, Dc = 1.288 g/cm3,μ（MoKα） = 0.178 mm^-1 and F（000） = 1831. The independent part of the unit cell contains two eprosartan molecules and one unordered H2O molecule in the crystal structure which is fixed by inter- and intramolecular hydrogen bonds. The product ions in electrospray ionization tandem mass spectrometry （ESI-MSn） displays the protonated eprosartan dissociated in three competitive pathways and the fragmentation mechanism is proposed and supported by the FTICRMSn results.     

Synthesis of 5‐substituted 1H‐tetrazoles using a recyclable heterogeneous nanonickel ferrite catalyst

An efficient method was developed for the [2 + 3] cycloaddition of sodium azide with nitriles to afford 5‐substituted 1H‐tetrazoles using nanonickel ferrite (NiFe₂O₄) as an effective heterogeneous catalyst in dimethylformamide. The main advantages of this method are high yields, simple methodology and easy work‐up. The catalyst can be recovered and reused for several cycles with predictable activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Fragmentation studies of sartans by electrospray ionization mass spectrometry

Sartans and related analogues with 5‐oxo‐l, 2, 4‐oxadiazole ring and tetrazole ring are investigated in detail using collision‐induced dissociation (CID) method in positive ion mode by electrospray ionization tandem mass spectrometry (ESI‐MSⁿ). It is found that the protonated sartans and related analogues tend to form the N‐substituted‐3‐substituted phenanthridin‐6‐amine ion which has a large conjugative structure. The possible fragmentation pathways were proposed for the first time, and the key structure of product ions was confirmed by high resolution tandem mass spectrometry and theoretical calculation. It is very helpful for understanding the intriguing roles of sartans analogues in fragmentation reactions and enriching the knowledge of the gas‐phase chemistry of the oxadiazole and tetrazole ring. Copyright © 2017 John Wiley & Sons, Ltd.     

聚酰胺类DNA识别分子质谱的碎裂机理

采用ESI-MS法研究了8个含有N-甲基吡咯(Py)和N-甲基咪唑(Im)杂环的聚酰胺质谱的特征和碎裂机理. MSⁿ数据表明, 聚酰胺化合物的主要碎裂路径是环与环间化学键的断裂, 即C—CO键、CO—NH键、HN—C键的断裂, 同时伴随着H原子的重排. 利用这些碎裂特征, 可以得到聚酰胺丰富的结构信息和区分它们的两种同分异构体.     

Synthesis of 5-substituted 1H-tetrazoles catalyzed by ytterbium triflate hydrate

Various 5-substituted 1H-tetrazoles were synthesized from aryl nitriles, alkyl nitriles, and vinyl nitriles reacting with sodium azide. The tetrazoles were recovered in high yield under mild conditions when the reaction was catalyzed by ytterbium triflate hydrate in dimethylformamide. Other rare-earth and post-transition metal catalysts were also investigated.     

Fragmentation studies of pentacoordinated bisaminoacylspirophosphoranes by negative electrospray ionization mass spectrometry

Fragmentation pathways of a series of pentacoordinated bisaminoacylspirophosphoranes were elucidated by electrospray ionization multistage mass spectrometry (ESI-MS(n)) in negative mode. The deprotonated ions of pentacoordinated bisaminoacylspirophosphoranes tend to eliminate a corresponding amino acid to form base peak. The hydrogen/deuterium exchange experiment, the high-resolution mass spectrometry, (13)C stable isotope labeling experiment and theoretical calculations were used to rationalize the proposed fragmentation pathways and to verify the differences between the fragmentation pathways. The results indicate that the negative molecular ions of pentacoordinated bisaminoacylspirophosphoranes dissociate through its open-chain tricoordinated tautomers. The relative Gibbs free energies (ΔG) of the product ions and proposed fragmentation pathways were estimated using the B3LYP/6-31 + + G(d, p) model. The results have some potential applications in the identification structures of similar spirophosphorane compounds by ESI-MS(n).     

Fragmentation of deprotonated cyclic dipeptides by electrospray ionization mass spectrometry

The fragmentation pathways of deprotonated cyclic dipeptides have been studied by electrospray ionization multi‐stage mass spectrometry (ESI‐MSⁿ) in negative mode. The results showed that the fragmentation pathways of deprotonated cyclic dipeptides depended significantly on the different substituents, the side chains of amino acid residues at the diketopiperazine ring. In the spectra of deprotonated cyclic dipeptides, the ion [M? H? substituent radical]^? was firstly observed in the ESI mode. The characteristic fragment ions [M? H? substituent radical]^? and [M? H? (substituent? H)]^? could be used as the symbols of particular cyclic dipeptides. The hydrogen/deuterium (H/D) exchange experiment, the high‐resolution mass spectrometry (Q‐TOF) and theoretical calculations were used to rationalize the proposed fragmentation pathways and to verify the differences between the fragmentation pathways. The relative Gibbs free energies (ΔG) of the product ions and possible fragmentation pathways were estimated using the B3LYP/6–31++G(d, p) model. The results have some potential applications in the structural elucidation and interpretation of the mass spectra of homologous compounds and will enrich the gas‐phase ESI‐MS ion chemistry of cyclic dipeptides. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of 5-substituted 1H-tetrazoles catalyzed by ceric ammonium nitrate supported HY-zeolite

In this Letter we wish to report a simple and efficient synthetic protocol for the synthesis of 5-substituted 1H-tetrazole derivatives through the [2+3] cycloaddition of nitriles with sodium azide using ceric ammonium nitrate supported HY-zeolite as a novel catalyst. Excellent yields of the corresponding tetrazoles were obtained through this cost-effective protocol under aerobic conditions with shorter reaction time under mild reaction conditions.     

5-乙酰(苯甲酰)基-4-芳基-3,4-二氢嘧啶-2(1H)-酮的质谱裂解规律

Using high resolution capabilities of a time-of-flight instrument and ion trap tandem technique, electron impact mass spectra of 5-acetyl (benzoyl)-4-aryl-3,4-dihydropyrimidin-2 (1H)-ones 1-5 were studied. The molecular ion (M) peaks for 1-3 can be found in the spectra with high abundances, but very weak for 4 and 5,in which strong electron-attracting substituents are attached to the benzene ring. The main fragmentation pathways for 1-5 include the cleavage of (M-Ar) + with high intensity, (M-RCO) + with moderate abundance, (M-H) +with high intensity for the compounds without strong electron-attracting substituent in the aromatic ring, and the pyrimidine ring cleavage (loss of neutral NH=C=X). In addition, a prominent cation (Ph + , m/z 77) can be found in the low mass region of the spectra for all the compounds, which give rise by different pathways between 1- 2 and 3-5. Several additional fragmentations for individual compounds are proposed.     

Dendrimer Disassembly in the Gas Phase: A Cascade Fragmentation Reaction of Fréchet Dendrons

The mass spectrometric characterization of Fréchet‐type dendrons is reported. In order to provide the charges necessary for electrospray ionization, dendrons bearing an OH group at the focal point can be deprotonated and observed in the negative ion mode. Alternatively, the corresponding bromides can be converted to quaternary ammonium ions that can easily be detected in the positive mode. If the latter ions are subjected to collision‐induced dissociation experiments, a fragmentation cascade begins with the dissociation of the focal amine. The focal benzyl cation quickly decomposes in a fragmentation cascade from the focal point to the periphery until the peripheral benzyl (or naphthylmethyl) cations are formed. Five different mechanisms are discussed in detail, three of which can be excluded based on experimental evidence. The cascade fragmentation is reminiscent of self‐immolative dendrimers.     

Zinc chloride catalyzed synthesis of 5-substituted 1H-tetrazoles under solvent free condition

Zinc chloride is an efficient and safe catalyst in the[3 + 2]cycloaddition reaction of organic nitriles with sodium azide in solventless condition.The corresponding S-substituted 1H tetrazoles were obtained under mild conditions.This method can overcome disadvantages such as:the use of toxic metals and expensive reagents,drastic reaction conditions,water sensitivity and the presence of dangerous hydrazoic acid.     

Non-catalyzed addition of heterocyclic thiols and 5-substituted-1H-tetrazoles to vinyl ethers

The alkylation of 1-substituted 1H-tetrazole-5-thiols and 4-substituted 4 H-1,2,4-triazole-3-thiols with alkyl halides or sulfonates lead to the formation of S-alkylated products regardless of the substituent on the heterocycle. In this work, we found that substituted 1H-tetrazole-5-thiols and 4 H-1,2,4-triazole-3-thiols readily reacted with vinyl ethers in the absence of a catalyst to exclusively form N-substituted 1H-tetrazole-5(4H)-thiones and 1H-1,2,4-triazole-5(4H)-thiones, respectively. Furthermore, the reactions of 5-substituted-1H-tetrazoles with vinyl ethers under the same conditions selectively yielded 2,5-disubstitued tetrazoles.