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运用密度泛函理论的B3LYP方法对1-碘-2-锂-邻碳硼烷与亚甲基环戊二烯衍生物的类Diels-Alder反应进行了理论研究.计算结果显示:1-碘-2-锂-邻碳硼烷与亚甲基环戊二烯衍生物的类Diels-Alder反应为分步过程,需要依次经过脱LiI形成碳硼炔、碳硼炔与亚甲基环戊二烯成键、碳硼烷基1,2-σ迁移和成环四个过程才能形成与Diels-Alder反应形式相同的产物.其中碳硼烷基的1,2-σ迁移过程为整个反应的决速步,在353 K的实验条件下需要越过28.3 kcal•mol-1的自由能垒才能形成相应的碳硼烷基降冰片烯衍生物,理论预测的反应速率与实验结果较好吻合.自然键轨道理论(NBO)分析结果显示:该反应与正常电子需求的Diels-Alder反应(NEDDA)具有相似的电子结构特征.文中还对反应底物的取代基效应进行了讨论,并得到了与实验数据基本一致的结果. 相似文献
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五甲氧羰基环戊二烯基钾和取代苄基卤化物反应, 合成了七个新型苄基取代五甲氧羰基环戊二烯。由^1H NMR、IR、元素分析等确认R(苄基)和环戊二烯上碳直接相连, 具有典型的碳碳连结。对产物之一, 1-萘亚甲基五甲氧羰基环戊二烯的X射线衍射测定, 进一步肯定了上述结论。化合物为单斜晶系, 空间群为P2/n, a=0.9731(1), b=1.7403(3), c=1.465(3)nm; β=95.70(1)^°, v=2.4712nm^3, D~c=1.334g/cm^3, 最终的R=0.093, 萘亚甲基环与环戊二烯基环的二面角为68.19^°。 相似文献
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关环转换反应是形成碳碳双键的重要反应之一,即双烯化合物在金属碳烯催化下关环得到环烯类化合物。本文概述了关环转换反应所用催化剂体系及其在天然产物合成中的应用,内容涉及到碳环及含氧、含氮杂环天然产物的合成。 相似文献
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由三甘醇和四甘醇出发,经炔丙基烷基化、Mitsunobu反应和Eglinton偶联反应3步合成了2个含均苯四甲酸二酰亚胺结构单元以及丁二炔结构单元的大环化合物,关环产率分别为81%和85%.大环化合物及中间体的化学结构经核磁共振氢谱、碳谱、低分辨质谱、高分辨质谱或元素分析等确认.通过氘代丙酮中1HNMR实验以及氯仿中紫外滴定实验研究了这类大环化合物与客体分子四硫富瓦烯(TTF)和1,5-二甲氧基萘(DNP)在溶液中的相互作用,结果发现,大环化合物的核磁化学位移及紫外光谱均发生变化.通过得到的主-客体间的络合常数可知,此类新型大环化合物与TTF和DNP之间有一定的络合作用. 相似文献
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Alan R. Katritzky Richard D. Tarr Steven M. Heilmann Jerald K. Rasmussen Larry R. Krepski 《Journal of polymer science. Part A, Polymer chemistry》1988,26(12):3323-3336
The following reactions of pyrylium salts with amines are described: (1)bis(pyrylium salts) with amines; (2) diamines with pyrylium salts; and (3) bis(pyrylium salts) with diamines. Both (1) and (2) give bis(pyridinium salts) in high yields, and (3) gives the corresponding polymers which are isolated and characterized. This procedure was applied to cationic bis(pyrylium salts) to give cationic dimers and polymers, and further to zwitterionic bis(pyrylium salts) to yield the corresponding zwitterionic dimers and polymers. 相似文献
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G. N. Dorofeenko G. A. Korol'chenko S. V. Krivun 《Chemistry of Heterocyclic Compounds》1966,1(6):551-554
A method of synthesizing pyrylium salts with heterocyclic substituents in the ring, has been investigated. The synthesis was carried out in two stages: alkaline condensation of aromatic and heterocyclic aldehydes with methyl ketones to give 1, 5-diketones, followed by cyclization to pyrylium salts by treatment with triphenylmethyl perchlorate. Pyridines containing heterocyclic substituents were obtained by treating the pyrylium salts with ammonia. 相似文献
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Juliusz Pernak Anna ?wierczyńskaMariusz Kot Filip WalkiewiczHieronim Maciejewski 《Tetrahedron letters》2011,52(33):4342-4345
Pyrylium salts represent a new group of ionic liquids (ILs) containing a positive charge on the oxygen atom. The novel ILs were obtained starting with 4-pyrones from petroleum feedstock and renewable resources and sulfonic acids. The use of carboxylic acids instead of salts resulted in the formation of cocrystals. The synthesized pyrylium ionic liquids were stable in air and in contact with water and common organic solvents. The permanganate indices which are characteristic for prepared sulfonates were also investigated. The pyrylium ionic liquids were useful as immobilizers and dissolving agents in hydrosilylation reactions. 相似文献
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The structural elucidation by NMR spectroscopy of trisubstituted α-pyridones and the isomeric 2-amino-γ-pyrones as well as their internal and external pyrylium salts is described. The most useful parameter for the differentiation between α-pyridones and isomeric γ-pyrones is the geminal coupling constant 2J(C-6, H-5) which changes from ~2.5 Hz to ~7 Hz whenever the cyclic amide group is replaced by an oxa-function; this applies to both the γ-pyrones and their pyrylium salts. The value of J(C-6, H-5) in the pyridones resembles that of the analogous coupling in N-vinylacetamide, whose sign determination by the selective population inversion (SPI) technique is reported. The 13C chemical shifts of seven pyridones, pyrones and pyrylium salts are reported and their structural correlations are discussed. Quick structural assignments in these classes of compounds may also be performed by evaluating the 14N chemical shifts, which often are accessible by the {14N}—1H-INDOR technique. The proton coupled 13C NMR spectra of two tetrasubstituted pyridines are also reported, and empirical correlations between long range C? H coupling constants and substituent electronegativity are discussed. 相似文献
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2,4,6-Trisubstituted pyrylium salts containing a cymantrenyl substituent in the 6 position were synthesized by condensation of acetylcymantrene with chalcones. As compared with the corresponding pyrylium derivatives of ferrocene, the pyrylium salts obtained exchange a heteroatom more readily and are more stable. The pyrylium derivatives of cymantrene were converted to the corresponding pyridines by the action of ammonium acetate in glacial acetic acid or an aqueous solution of ammonia and to the corresponding N-phenylpyridinium salts by the action of aniline in acetic acid or alcohol.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 21–24, January, 1979. 相似文献
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Liviu Birzan Mihaela Cristea Constantin C. Draghici Victorita Tecuceanu Anamaria Hanganu Eleonora-Mihaela Ungureanu Alexandru C. Razus 《Tetrahedron》2017,73(17):2488-2500
The synthesis of pyrylium and pyridinium salts and pyridines with azulene-1-yl moieties in position 4 and two 2-heteroarylvinyl groups in positions 2 and 6 was accomplished. The pyrylium salts were obtained starting from pyranones and pyridines could be prepared from these salts by treating them with ammonium acetate. The general procedures for the synthesis of pyridinium salts, which occur with good results in less delocalized electronic systems, do not take place when applied to the above obtained pyrylium salts. Therefore, as starting material 4-(azulen-1-yl)-1-(n-butyl)-2,6-dimethylpyridinium perchlorate was used, which was condensed with heteroarylcarboxaldehydes. These compounds were completely characterized and some of their spectra were discussed. Their interaction with some metal ions was revealed, observing an affinity better than in the case of simple azulenepyridines. In the last part of the paper are presented redox potentials for several pyrylium salts and pyridines in comparison with those of the nonvinylogated derivatives. 相似文献
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Alan R. Katritzky Charles M. Marson 《Angewandte Chemie (International ed. in English)》1984,23(6):420-429
The first pyrylium salt was isolated some 80 years ago, yet up to the 1950s only moderate interest was taken in the preparation, properties and uses of such salts. However, the past thirty years has seen a phenomenal growth in the literature pertinent to this area of chemistry: the importance of pyrylium salts as intermediates has been realized. They are readily prepared by a variety of generally applicable routes, and they are highly reactive towards nucleophiles. Together, this enables the convenient synthesis of a great variety of acyclic and heterocyclic compounds. We have used highly substituted pyrylium salts for the two-step conversion of the amino group in alkylamines RNH2 into numerous other functionalities. In the first step, the pyrylium salts are converted with the amines into N-substituted pyridinium salts, which, in the second step, react with Nu? to give the desired products RNu. In some cases the R moiety is also changed, e.g. by elimination. Studies of the reactions of these pyridinium salts have allowed interesting insights into the mechanisms of nucleophilic substitution, in addition to rendering aliphatic amines important synthetic intermediates. Thus, the method complements the diazotization procedure for the transformation of arylamines. 相似文献
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S. Sib 《Tetrahedron》1975,31(18):2229-2235
Secondary amines react with 2,4-dialcoxy 6-méthyl pyrylium salts to give two new series of 2-amino and 2,4-diamino pyrylium cations. 2,4-Dialkoxy pyrylium salts react as alkylating reagents. A comparison with 1,3-dialcoxy carbonium cations reactivity is reported. 相似文献
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Polyzos I Tsigaridas G Fakis M Giannetas V Persephonis P Mikroyannidis J 《The journal of physical chemistry. B》2006,110(6):2593-2597
The current article presents the photobleaching properties of a group of pyrylium salts under ultrashort pulsed illumination. These pyrylium salts have the same basic chemical structure and differ only by a specific substituent. It is proven experimentally that two different mechanisms are simultaneously present to the photobleaching of all molecules studied (independently of their specific chemical structure). However, the particular parameters of each mechanism are influenced significantly by the substituent change. The experimental investigation of these parameters showed the presence of multiphoton interactions in the photobleaching of pyrylium salts depending essentially on the specific substituent. 相似文献
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By the reaction of lithium derivatives of cyclopentadienylmagnesiumtricarbonyl, cyclopentadienylrheniumtricarbonyl, and benzenechromiumtricarbonyl with 2,6-disubstituted pyrylium salts the corresponding 4H-pyrans have been synthesized, and the oxidative dehydration of these has given pyrylium cations containing the stated organometallic groups in position 4. It has been shown that the -complexes obtained readily exchange the oxygen of the pyrylium ring for other heteroatoms with the formation of heterocyclic compounds with metallocarbonyl substituents.Translated from Khimiya Geterosiklicheskikh Soedinenii, No. 5, pp. 593–597, May, 1985. 相似文献