化学修饰在质谱中的应用 3: 环丙烷脂肪酸的苯并 唑衍生物的质谱特征

本文作者曾成功地利用苯并 唑衍生物直接鉴定出不饱和脂肪酸中酸双键位置。本文在该基础上继续研究了长链环丙烷酸的苯并 唑衍生物的质谱, 结果证明脂肪链上的环丙烷基部位在其质谱上可得到特征的反映, 根据谱中碳链系列离子峰的质量间隔, 就可确定出环丙烷基在脂肪链的位置。     

化学修饰在质谱中的应用 I:长链不饱和脂肪酸的双键定位: 2-烯基取代杂环化合物的质谱

作者提出了一种用"远端基团修饰法"来确定双键位置的新途径.长链不饱和脂肪酸环化为相应的2-烯基杂环化合物后,这些杂环母核的强大的正荷定域作用使产物的质谱的结构专一性大为提高,并能直接提供有关双键位置的信息.本文报道了微量衍生化方法与八类代表性杂环衍生物与四种苯并唑衍生物的质谱比较.     

化学修饰在质谱中的应用 3.环丙烷脂肪酸的苯并噁唑衍生物的质谱特征

环丙烷脂肪酸是种子油脂和细菌脂质的重要组成部分。人们曾用质谱来确定链上环丙烷的位置,然而位置异构的环丙烷酸以及简单的衍生物(如甲酯)的质谱特征极不明显,因而不能用于鉴别的目的。化学修饰是用来改善谱形并增加谱中结构信息的一种重要方法。文献报道用氢解或其它反应来使环丙烷环开裂,或借助于“远端修饰”(“remote site modifica-tion”)将环丙烷酸中的羧基改变成相应的四氢吡咯酰胺或菸醇酯再进行质谱分析,以判断环丙烷基的位置。这些方法操作不便或图谱特征不强,因而需要寻找更有效的鉴定方法。     

化学修饰在质谱中的应用 Ⅰ.长链不饱和脂肪酸的双键定位——2-烯基取代杂环化合物的质谱

作者提出了一种用“远端基团修饰法”来确定双键位置的新途径.长链不饱和脂肪酸环化为相应的2-烯基杂环化合物后,这些杂环母核的强大的正荷定域作用使产物的质谱的结构专一性大为提高,并能直接提供有关双键位置的信息.本文报道了微量衍生化方法与八类代表性杂环衍生物与四种苯并噁唑衍生物的质谱比较.     

第五、六族元素的有机化合物在有机合成中应用的研究Ⅺ.三取代环丙烷的质谱研究

本文报道12种三取代环丙烷的质谱及其解析结果.讨论了不同取代的环丙烷衍生物的断裂方式及质谱规律.     

含氟异(口恶)唑类化合物的质谱研究

异噁唑类化合物的质谱已有报道,该类化合物在电子轰击下易发生环内N—O键断裂,同时发生由异噁唑转变为氮杂环丙烷或嗯唑的重排.本文报道19个含氟异噁唑的EI质谱,研究了它们在电子轰击下的碎裂机理,观察到甲基、苯氧基和氟原子的重排. 19个含氟异噁唑化合物的结构式如下:     

己二酰肼脂肪族双酰基衍生物的电子轰击电离质谱特征

前文曾报道了己二酰二肼脂肪族双酰基衍生物的金属减活作用 [1] ,在研究中还发现该类化合物在电子轰击电离 (EI)条件下的质谱裂解行为具有特征的规律 .因为 ,在已研制和开发的酰肼类金属减活剂中 ,— NHNH—的封端为芳环者较多 ,为脂肪族碳链者甚少 [2 ,3 ] ;而且该类化合物还是合成具有生物活性及电子传输功能的双 - 1 ,3 ,4-二唑的重要前体 ,正在重新引起重视 [4 ,5] ;再则它们的溶解性普遍很差且使用时浓度较小 ,所以关于该类化合物结构表征的波谱学研究并不多见 .本文报道了己二酰肼脂肪族双酰基衍生物的 EIMS特征 ,对于该类化合…     

α-卤代酮在银粉作用下的反应

研究了用银粉和碘化钾在无水丙酮中处理α-溴代乙酰苯酮及其环取代衍生物.反应结果得到α,β-环氧酮,1,2,3-三苯酰基环丙烷,2,4-二苯基呋喃,1,4-二酮类及其它产品,并用柱色谱分离,α-溴代乙酰苯酮与芳香醛和1,4-二苯基丁烯-2-二酮-1,4的反应也被研究了.     

氮杂多环光致发光分子用于食品中脂肪胺的分析及质谱鉴定

对含氮类光致发光分子2-（11H-苯[a]咔唑）-异丙基氯甲酸酯进行柱前衍生处理,并经荧光检测对脂肪胺进行高效液相色谱（HPLC）分离和质谱定性。衍生物于λex=279nm产生强烈荧光,发射波长为λex=380nm。40℃下在pH9．0的硼酸缓冲液中,衍生反应3min后获得稳定的荧光产物。在Eclipse XDB-C8色谱柱（4．6mm×150mm,5μm）上,采用梯度洗脱对12种脂肪胺衍生物进行了优化分离。采用大气压化学电离源（APCI Source）正离子模式进行质谱定性,实现了各种脂肪胺衍生物的快速、准确测定。该方法具有良好的重复性,多数脂肪胺的线性回归系数大于0．9994,检出限在2．73～23．16fmol水平。     

反-1,2-双 二唑基取代环丙烷的合成与环丙烷环的不饱和性

本文合成了一个新的反-1,2-双芳杂环取代的环丙烷类化合物─反-1,2-双-2'-[5'-(对乙基苯基-1',3',4'- 二唑基)]环丙烷(Et-BDCP), 研究了其紫外吸收光谱及其荧光激发与发射光谱, 并通过与Et-BPDS, Et-BPDE和Et-PDDDP光谱性质的比较; 以及用MNDO方法对模型化合物(1-8)所进行了模拟量子化学计算, 证明了环丙烷环可以在某种程度上与不饱和体系共轭。     

反-1,2-双 二唑基取代环丙烷的合成与环丙烷环的不饱和性

本文合成了一个新的反-1,2-双芳杂环取代的环丙烷类化合物─反-1,2-双-2'-[5'-(对乙基苯基-1',3',4'- 二唑基)]环丙烷(Et-BDCP), 研究了其紫外吸收光谱及其荧光激发与发射光谱, 并通过与Et-BPDS, Et-BPDE和Et-PDDDP光谱性质的比较; 以及用MNDO方法对模型化合物(1-8)所进行了模拟量子化学计算, 证明了环丙烷环可以在某种程度上与不饱和体系共轭。     

Palladium-catalyzed oxidative activation of arylcyclopropanes

Palladium chloride-catalyzed intramolecular activation of electroneutral cyclopropane derivatives results in cleavage of the cyclopropane ring followed by formation of heterocyclic derivatives. Phenols, carboxylic acids, and amide groups were considered as substituents ortho to the cyclopropane ring in this catalytic activation chemistry. The regioselectivity observed in the case of amide-containing substrates was different from that of carboxylic acid-containing substrates, ruling out simple cyclopropane isomerization followed by a Wacker oxidation as the mechanistic pathway. [reaction: see text]     

1,1-Dihalo-2-benzycyclopropanes in reaction with nitrous acid

Interaction of 1,1-dichoro and 1,1-dibromo-2-benzylcyclopropanes with nitrous acid generated in situ was studied. It was shown that both nitration of the aromatic ring and heterocyclization of 1,1-dihalo-2-benzylcyclopropanes take place. Heterocyclization is initiated by opening of the cyclopropane ring in the reaction with nitrosyl cation. The nature of halogen atom in the cyclopropane ring affects the regioselectivity of the reactions.     

Bonding Properties of Cyclopropane and Their Chemical Consequences

Among the cyclic compounds of carbon, cyclopropane and its derivatives are outstanding by virtue of their unusual structural, spectroscopic, and chemical properties. The cyclopropane ring more closely resembles the C?C double bond than the cyclobutane ring: it is a small ring with “double bond character”. Cyclopropyl and vinyl groups interact with neighbouring π-electron systems and p-electron centers; both cyclopropane derivatives and olefins form metal complexes, and add strong acids, halogens, and ozone; they both undergo catalytic hydrogenation and cycloadditions. While distinct differences in reactivity do exist–the double bond usually being more reactive than the three-membered ring–there are no fundamental differences in behavior.–Although cyclopropane derivatives have been known for more than 90 years, intensive studies have been limited to the past 25 years. The development of carbene chemistry has rendered cyclopropane derivatives far more readily accessible. In recent years, the synthetic potential of the small-ring function has been increasingly exploited. A considerable number of newly developed methods utilizing this approach clearly demonstrates that the reactivity of the cyclopropene ring, like that of the C?C double bond, qualify it as a “functional carbon group”. This development is in full swing; we may therefore justifiably devote considerable effort to the study of cyclopropane chemistry.     

Three-carbon ring expansion by cyclopropane insertion: macrocyclic musks from readily available C-12 starting materials

A thermal three-carbon ring expansion based on side chain ring insertion of a cyclopropane moiety is described. Flash vacuum pyrolysis (FVP) of 1-cyclopropyl-cycloalk-3-enol derivatives leads to the three-carbon ring expanded enones with clean retention of double bond geometry. Substrates bearing methyl groups on the cyclopropane ring undergo regioselective bond cleavage, allowing for the systematic preparation of selectively substituted macrocyclic musks from low-priced C-12 starting compounds.     

Visible‐Light Photocatalytic Intramolecular Cyclopropane Ring Expansion

Described herein is a new visible‐light photocatalytic strategy for the synthesis of enantioenriched dihydrofurans and cyclopentenes by an intramolecular nitro cyclopropane ring expansion reaction. Mechanistic studies and DFT calculations are used to elucidate the key factors in this new ring expansion reaction, and the need for the nitro group on the cyclopropane.     

Visible-Light Photocatalytic Intramolecular Cyclopropane Ring Expansion

Described herein is a new visible-light photocatalytic strategy for the synthesis of enantioenriched dihydrofurans and cyclopentenes by an intramolecular nitro cyclopropane ring expansion reaction. Mechanistic studies and DFT calculations are used to elucidate the key factors in this new ring expansion reaction, and the need for the nitro group on the cyclopropane.     

Nickel-catalyzed regio- and stereoselective reductive coupling between methylenecyclopropanes, aldehydes, and triethylborane with retention of the cyclopropane ring

Running rings: The first regio- and stereoselective reductive coupling between methylenecyclopropanes, aldehydes, and triethylborane with retention of the cyclopropane ring was achieved using a nickel-phosphine catalyst (see scheme). The reductive coupling reaction constructed a stereo-defined cyclopropane ring with formation of a quaternary stereogenic carbon center.     

Reactions of methylated cyclopropanes and olefins with chloroplatinic acid. I. Diacylation and pyrylium ion formation

In contrast to cyclopropane itself, simple methyl-substituted cyclopropanes do not produce platinum insertion products upon reaction with chloroplatinic acid in acetic anhydride. Instead, the major products are aromatic heterocyclic cations, the pyrylium ions, which are formed as the result of diacylation of the cyclopropane ring and subsequent dehydration and ring closure to the aromatic heterocycle. Similar products are formed from the diacylation of certain olefins in the presence of chloroplatinic acid in anhydride solvents. The combination of solvent and substrate variations has led to a proposed mechanism for these reactions which demonstrates the essential and unique mole of platinum. In particular, the specific pyrylium ions produced are formed as a consequence of initial activation of the least-substituted cyclopropane ring bond by insertion of platinum, followed by acylation of platinum-bonded carbon, proton loss to a β,γ-unsaturated carbonyl, a second acylation, and, finally, ring closure.