AuCl_3催化2-丙炔基-苯胺和丙炔反应机理的研究

采用密度泛函理论方法B3PW91研究了AuCl3催化剂作用下2-丙炔基-苯胺和丙炔环加成生成吲哚衍生物的反应机理。研究结果表明,吲哚衍生物的生成需要经过六个步骤,其中氢迁移过程具有最高的活化自由能为214.22 kJ/mol,是反应的速率控制步骤。整个反应是强放热的,AuCl3催化下反应能够顺利进行,而且AuCl3易于从产物上离去,所以,对于该反应AuCl3是一种有效的催化剂。     

吲哚与亚胺的Friedel-Crafts反应的研究进展

由于吲哚类化合物具有许多生物特性等优点,在众多天然产物和相应的具有生物活性的化合物中起重要的骨架构筑作用,其合成方法的研究格外令人注目.近年来,关于吲哚与亚胺在催化剂作用下发生Friedel-Crafts反应来制备3-取代吲哚甲胺衍生物的报道剧增.对近年来吲哚与亚胺Friedel-Crafts反应的研究情况进行了综述.     

吲哚类生物碱的合成研究进展

吲哚类生物碱是具有吲哚分子骨架的一类化合物,具有多种良好的生理活性。文章综述了近年来新发现吲哚类生物碱的合成研究进展,介绍了(-)-Arboricine,(±)-cis-Trikentrin A,(-)-Corynantheidol等化合物的合成方法。     

酸性离子液体催化合成三吲哚甲烷化合物

在酸性离子液体催化下,通过吲哚及其衍生物和吲哚甲醛反应合成了一系列三吲哚甲烷化合物。[hmim]HSO₄/EtOH 对于该反应来说,是一个高效、绿色的催化体系。     

稀土吲哚-3-乙酸和吲哚-3-丁酸配合物的合成、表征及成键特性研究

在乙醇水溶液体系中合成了8种新的稀土吲哚-3-乙酸和吲哚-3-丁酸配合物,其通式为Ln(lA)_3·2H_2O和Ln(IB)_3·2H_2O(Ln=La,Nd,Sm,Er;IA=C_(10)H_8NO_2;IB=C_(12)H_(12)NO_2)。用元素分析、电导测定、电子吸收光谱、红外光谱、X光电子能谱和热重-差热分析确定了配合物的组成和成键特性。     

喜树中的吲哚生物碱

从喜树(Camptetheca acuminata Decne)果中分到五个微量吲哚类生物碱, 其中两个为新生物碱, 分别为camptacumotint(1)和camptacumanine(2), 另外三个为已知生物碱naucleficine(3), angustoline(4)和新天然产物二氢异喹胺(dihydroisoquinamine, 5).     

一类新的吲哚酮衍生物的合成和可见光谱

吲哚酮衍生物是一类重要的杂环化合物,尤其在杂环染料上。最近,Griffiths 等报道了茚三酮核上连接有偶氮基的新型的在近红外有吸收的染料,因此在吲哚酮环发色团上接上各种助色团就引起了人们的兴趣。众所周     

光诱导有机化合物异构化反应的研究——Ⅹ. 吲哚啉螺吡喃瞬态吸收光谱的研究

研究了1-正-辛基-3,3-二甲基-吲哚啉-2,2′-螺-5′,6′-(2-溴-4-硝基-苯并)吡喃, 1-正-辛基-3,3-二甲基-吲哚啉-2,2′-螺-5′,6′-(4-硝基-苯并)吡喃, 1-正-辛基-3,3-二甲基-吲哚啉-2,2′-螺-5′,6′-(2,4-二硝基-苯并)吡喃及1-正-辛基-3,3-二甲基-吲哚啉-2,2′螺-5′6′-(2-氯-4-硝基-苯并)吡喃在环已烷和甲苯溶液中光致开环过程的瞬态吸收光谱。观察到具有较长寿命的中间体及聚集体的存在。初步提出异构化反应过程的机制中既包含有三重态过程, 也有单重态参与。     

长链双吲哚啉螺苯并吡喃的合成

吲哚啉螺吡喃是一类重要光(热)致变色化合物,在现代技术和日用工业中已有应用。70年代以来人们已制得各种类型的双螺吡喃,但由于溶解性能较差等原因使其应用开发受到限制。向母体分子中引入长链烷基是改善与树     

Thermo-chemical reactions and structural evolution of acrylamide-modified polyacrylonitrile

<正>Thermal properties of acrylonitrile(AN)-acrylamide(AM) copolymers for carbon fibers were studied by DSC and in situ FTIR techniques in nitrogen(N_2) and air flows.The cyclization mechanism and stabilization behavior of polyacrylonitrile(PAN) were discussed.In N_2 flow,it was found that AM had the ability to initiate and accelerate cyclization process,which was confirmed by the fact that the initiation of nitriles shifted to a lower temperature.Compared to AN homopolymer,the initiation temperature of cyclization was ahead 32 K by introducing 3.59 mol%AM into the copolymer.The exothermic reaction was relaxed due to the presence of two separated exothermic peaks.Accompanied by DSC,in situ FTIR and calculation of activation energy,the two peaks were proved to be caused by ionic cyclization and free radical cyclization,respectively,and the corresponding cyclization mechanism was proposed.With increasing in AM content,the ionic cyclization tends to be dominant and the total heat liberated first increases and then decreases.For AN homopolymer,the activation energy of cyclization is 179 kJ/mol.For AN-AM copolymer(containing 3.59 mol%AM),the activation energy of ionic cyclization is 96 kJ/mol and that of free radical cyclization is 338 kJ/mol.In air flow,similar cyclization routes occur and the difference is the contribution of oxidation.The oxygen in environment has no remarkable effect on cyclization of AN homopolymer but retards the cyclization of AN-AM copolymers.For AN-AM copolymer with 3.59 mol%AM,the cyclization temperature is postponed 10℃in air.     

炔烃分子内环化反应合成含氮杂环化合物研究进展

分子内氮原子参与的炔烃环化反应是构成含氮杂环化合物(例如吲哚类化合物等)的最重要途径之一. 从两个方面对分子内氮杂原子与炔的环化反应研究新进展进行了综述: 过渡金属催化分子内环化反应和分子内亲电环化反应. 此外, 对环化反应的机理也做了较详细的描述.     

Regiochemistry in aryl radical cyclization onto methylenecycloalkanes

Bu(3)SnH-mediated aryl radical cyclization onto methylenecycloalkanes having a phenylthio, an ester, or a nitrile group at the terminus of the alkenic bond provides exclusively exo cyclization products. The results are in sharp contrast to those reported for nonsubstituted methylenecycloalkanes, which give exclusively endo cyclization products. Formation of endo cyclization products has been suggested to be a result of a consecutive 5-exo cyclization of an aryl radical and neophyl rearrangement. The exo-selective aryl radical cyclization offers a new method for synthesizing fused aromatic compounds containing a benzylic quaternary carbon atom.     

含内环化与不含内环化固化理论间的对应关系

含内环化与不含内环化固化理论间的对应关系黄旭日，肖兴才，李泽生，孙家，唐敖庆（吉林大学理论化学研究所，长春，１３００２３）关键词内环化，非线性缩聚反应，数量分布函数，高分子矩在研究非线性缩聚反应体系的固化问题时，Ｆｌｏｒｙ和Ｓｔｏｃｋｍａｙｅｒ等［１...     

Palladium‐Catalyzed Cascade Cyclization/Alkynylation Reactions

Palladium‐catalyzed cascade cyclization reactions have witnessed significant improvements in recent years. Among them, palladium‐catalyzed cascade cyclization/alkynylation are especially attractive, which can assemble structurally diverse monocyclic, bicyclic, fused polycyclic, and spirocyclic skeletons with excellent chemoselectivities. In this Minireview, palladium‐catalyzed cascade cyclization/alkynylation have been summarized and discussed in detail with focus on oxypalladation and aminopalladation‐initiated cascade cyclization, intramolecular Heck‐type cascade cyclization, carbocyclizations, cascade cyclizations, and other types of cascade cyclization reactions. Some significant and representative synthetic methodologies and their synthetic applications and reaction mechanisms have also been described.     

Promotion of cyclization of linear pentapeptides and heptapeptide by different univalent metal ions

Univalent metal ions such as Na+, K+ and Cs+ can enhance not only the cyclization yields of some linear pentapeptides and heptapeptide but also their cyclization rates while some bivalent and trivalent metal ions such as Mg2+, Ca2+, Zn2+, Fe2+, Ni2+ and Cr3+ elevate neither the cyclization yields nor the cyclization rates and some of them prevent the cyclization.     

Round trip radical reactions from acyclic precursors to tricyclo [5.3.1.0]undecanes. A new cascade radical cyclization approach to (+/-)-isogymnomitrene and (+/-)-gymnomitrene

The synthesis and "round trip radical cyclization" of 11-iodo-2,7,11-trimethyldodec-6-en-5-one are described. The round trip cyclization is a sequence of 5-exo, 6-endo, and 5-exo cyclizations in which the last radical cyclization occurs at the same carbon atom as the initial radical generation. The key second (6-endo) cyclization produces two stereoisomers, one of which cyclizes efficiently to isogymnomitrene ketone, while the other cyclizes inefficiently to gymnomitrene ketone. Efforts to influence the kinetic or thermodynamic outcome of the second cyclization were not successful, and the results are contrasted with a related cyclization of Jung and Rayle where thermodynamic control was readily established.     

The remarkable effect of cosolvent on a samarium(II)-mediated 4-exo-trig cyclization: further synthetic studies on pestalotiopsin A

A samarium(II)-mediated 4-exo-trig cyclization in which a remote stereocenter serves to control the facial selectivity of the cyclization is described. The apparent coordination of a tert-butyldimethylsilyl ether to the samarium center appears to give rise to the selectivity. The remarkable effect of the cosolvent, 2,2,2-trifluoroethanol, on the cyclization of this substrate, is also discussed. A stereoselective synthesis of the general class of gamma,delta-unsaturated aldehyde cyclization substrate is reported, and the utility of the cyclization is demonstrated in an approach to the fully functionalized core of pestalotiopsin A.     

Dependence of the cyclization behavior of multifunctional network molecules on molecular size

The tendency for cyclization of nonlinear network molecules is quantitatively expressed by the cyclization probability, defined as the ratio of cyclization to total reaction rate. In contrast to branching, the rate of cyclization depends on the configurational statistical mechanics of segments joining functional groups. Direct integration of the joint configurational probability density in the subspace of encounters yields the distribution of the number of configurationally formed intramolecular functional group encounters (nearest neighbors). Statistically independent network segments are assumed to obey the Gaussian statistics. A recursive relationship for the distribution of chain lengths is developed, and it is shown that for large molecular sizes this relationship tends to a limiting distribution. Corresponding average and standard deviation follow power law dependence on degree of polymerization (DP). With these results, cyclization probabilities are explicitly expressed as functions of DP. When segmental diffusion is the rate controlling factor, cyclization is similar to short range (or primary) cyclization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 861–870, 2005     

6-Endo-dig versus 5-exo-dig: Exploring Radical Cyclization Preference with First-, Second-, and Third-row Linkers using High-level Quantum Chemical Methods

As an expansion upon Baldwin rules, the cyclization reactions of hex-5-yn-1-yl radical systems with different first-, second-, and third-row linkers are explored at the CCSD(T) level via means of the SMD(benzene)-G4(MP2) thermochemical protocol. Unlike C, O, and N linkers, systems with B, Si, P, S, Ge, As, and Se linkers are shown to favor 6-endo-dig cyclization. This offers fundamental insights into the rational synthetic design of cyclic compounds. A thorough analysis of stereoelectronic effects, cyclization barriers, and intrinsic barriers illustrates that structural changes alter the cyclization preference by mainly impacting 5-exo-dig reaction barriers. Based on the high-level computational modeling, we proceed to develop a new tool for cyclization preference prediction from the correlation between cyclization barriers and radical structural parameters (e. g., linker bond length and bond angle). A strong correlation is found between the radical attack trajectory angle and the reaction barrier heights, i. e., cyclization preference. Finally, the influence of stereoelectronic effects on the two radical cyclization pathways is further investigated in stereoisomers of hypervalent silicon system, which provides novel insight into cyclization control.