γ-环糊精诱导的双2-萘甲酸三缩四乙二醇酯的分子内光二聚反应

本文研究了在水溶液中γ-环糊精诱导双2-萘甲酸三缩四乙二醇酯(N-P4-N)的分子内光二聚反应.γ-环糊精能够控制N-P4-N光二聚反应的区域选择性和立体选择性,反应只得到反式-头头结构的分子内类立方烷光二聚体,其对映体选择性达20.4%e.e.(在0.5℃时).     

γ-环糊精控制的2-氰基萘的光二聚反应

最新的研究发现2-氰基萘(CN)能够发生光二聚反应生成3种类立方烷结构的二聚体,anti-head-to-head 1、anti-head-to-tail 2和syn-head-to-tail 3.本文研究了水溶液中γ-环糊精对2-氰基萘的光二聚反应区域选择性的影响.结果表明,γ-环糊精(γ-CD)能够显著影响2-氰基萘的光二聚反应,在提高反应速率的同时,得到较好的区域选择性,室温下光照CN@γ-CD包结物水溶液,主要得到头-头产物1.     

羧基取代类立方烷结构的萘光二聚体与芳香胺的反应性

本文利用羧基取代类立方烷结构的萘光二聚体2与芳香胺3反应研究这类结构化合物的反应活性。X-单晶衍射分析表明二环已基碳二亚胺（DCC）与2生成了具有类立方烷骨架的稳定化合物4,而且DCC能够作为一种有效的缩合剂催化2与3的反应,得到单独用光化学方法或热化学方法都无法获得的单边缩合或双边缩合的类立方烷酰胺化合物5和6。研究发现芳香胺3的电子效应显著影响反应产物的分布。     

L(-)-α-苯乙胺拆分2-萘甲酸类立方烷光二聚体

使用L(-)-α-苯乙胺作为手性衍生化试剂,拆分了外消旋的类立方烷2-萘甲酸光二聚体,并通过圆二色谱进行了证明.     

γ-环糊精诱导的2-萘甲酸酯光二聚反应

本文研究了水溶液中γ-环糊精诱导2-萘甲酸酯的光二聚反应.γ-环糊精的限制性疏水空腔能够容纳两个2-萘甲酸甲酯(或乙酯)分子形成稳定的2:1包结复合物NA@γ-CD,光照NA@γ-CD包结物水溶液能高效、快速、高选择地生成2-萘甲酸酯的类立方烷光二聚体,并且该反应有一定程度的对映体选择性.     

L-(-)-α-苯乙胺类立方烷结构2-萘甲酸二聚体盐的晶体结构

L-(-)-α-苯乙胺与消旋的类立方烷结构2-萘甲酸二聚体相互作用形成铵盐,其晶体结构表明,L-(-)-α-苯乙胺与类立方烷结构2-萘甲酸二聚体作用形成的铵离子通过氢键N_2A-HN_2B…O_5A和N_1A-HN_1A…O_3A与类立方烷结构2-萘甲酸二聚体结合在一起.同时类立方烷结构2-萘甲酸二聚体的两个对映异构体之间也存在分子间氢键O_1A-H_1AA…O_6A和O_1B-H_1AB…O_6B.这些氢键将类立方烷结构2-萘甲酸二聚体的两个对映异构体连在同一个晶胞中,呈现两条分子链状堆积.     

9-乙烯基蒽和对-N,N-二甲氨基苯乙烯激基络合物的生成和光二聚反应

测定了9-乙烯基蒽和对-N,N-二甲氨基苯乙烯体系在不同极性的溶剂中的荧光光谱和荧光量子产率。发现随着溶剂极性的增加,激基络合物的荧光发生红移,荧光量子产率降低。同时9-乙烯基蒽和对-N,N-二甲氨基苯乙烯之间的光二聚产物的相对产率也降低。并讨论了经过激基络合物中间体的光二聚反应机理。     

3β-羟基-4,11-二烯桉烷酸甲酯的不对称全合成

近年来 ,从传统药用植物里分离出了很多桉烷酸类天然产物 ,它们绝大多数具有很好的杀菌、拒食等活性[1 ,2 ] .因此 ,对这一类天然产物的全合成研究成为当前的研究热点课题 .Ｓｃｈｅｍｅ 1　Ｔｈｅｓｔｒｕｃｔｕｒｅｏｆｃｏｍｐｏｕｎｄ 13β 羟基 4,1 1 二烯桉烷酸 (1 ,结构如Ｓｃｈｅｍｅ 1所示 )是德国化学家Ｂｏｈｌｍａｎｎ等[3] 从一种阿根廷的药用植物Ｓｔｅｖｉａａｃｈａｌｅｎｓｉｓ中分离得到的一个桉烷酸类天然产物 ,它的结构非常具有代表性 ,在反式十氢萘上共有 3个手性中心 ,其不对称全合成尚未见报道 .因此 ,如何高立体选…     

苯甲酰氧基取代的2-吡喃酮的固相光二聚反应

以二苯甲酮为光敏化剂,C4-位苯甲酰氧基取代的6-甲基-2-吡喃酮(1)的固相光二聚反应穿过1的C3-C4双键高选择性地发生[2+2]环加成反应合成了anti头-头二聚物(2),其结构经1H NMR,FI-IR,MS和元素分析表征。反应机理利用WINMOPAC PM5方法推定。     

苯乙烯基氮氧杂芳烃间的交叉光二聚反应

用中压汞灯(λ > 300 nm)照射4-苯乙烯基吡啶、2-苯乙烯基苯并噁唑和5-苯基-2-苯乙烯基噁唑三种杂芳基乙烯单体中任意两种的硫酸水溶液，得到三种交叉二聚体.用高效液相色谱跟踪研究了交叉光二聚反应，发现每组反应生成三种光二聚体，其中二种为单体自身的光二聚体，而另外一种是两种不同单体的交叉光二聚体.交叉二聚体通过柱色谱分离得到，其顺式头对尾结构经紫外、红外、氢谱、碳谱和元素分析确定.用紫外光谱和高效液相色谱跟踪研究了交叉光二聚体的稀溶液在低压汞灯（λmax=254 nm）照射下的光解反应.研究发现交叉二聚体能够彻底发生光解，首先生成原来的反式单体，所生成的反式单体容易发生异构化而生成顺式单体，最终建立起反顺异构化平衡.     

Self-assembled phenylethynylene bis-urea macrocycles facilitate the selective photodimerization of coumarin

There is much interest in designing molecular sized containers that influence and facilitate chemical reactions within their nanocavities. On top of the advantages of improved yield and selectivity, the studies of reactions in confinement also give important clues that extend our basic understanding of chemical processes. We report here, the synthesis and self-assembly of an expanded bis-urea macrocycle to give crystals with columnar channels. Constructed from two C-shaped phenylethynylene units and two urea groups, the macrocycle affords a large pore with a diameter of ～9 ?. Despite its increased size, the macrocycles assemble into columns with high fidelity to afford porous crystals. The porosity and accessibility of these channels have been demonstrated by gas adsorption studies and by the uptake of coumarin to afford solid inclusion complexes. Upon UV-irradiation, these inclusion complexes facilitate the conversion of coumarin to its anti-head-to-head (HH) photodimer with high selectivity. This is contrary to what is observed upon the solid-state irradiation of coumarin, which affords photodimers with low selectivity and conversion.     

Enantioselective [2 + 2] photodimerization reactions of coumarins in solution

[reaction: see text] The [2 + 2]photodimerization reactions of coumarin to an optically active anti-head-to-head dimer in the presence of an optically active host compound in cyclohexane solution proceeded with high enantioselectivity.     

Functional monomers and polymers. CXIX.. Synthesis and photochemical reaction of polymethacrylate derivative containing 6-cyanouracil

A polymethacrylate derivative containing 6-cyanouracil was prepared, and its photochemical reaction was studied. The 6-cyanouracil derivative was found to show high reactivity for the photochemiccal reaction. The photochemical-reaction product was identified as a cyclobutanetype photodimer, and the photodimer was formed in high yield even from the monomeric compound of 6-cyanouracil under UV irradiation in low concentration. The quantum yield of the photodimerization of the 6-cyanouracil derivative was greater than that of the thymine derivative. The photodimerization of the 6-cyanouracil derivative could not be quenched by usual triplet quenchers, but was found to be quenched by the polymeric derivative of adenine, suggesting a specific interaction.     

New organogels based on an anthracene derivative with one urea group and its photodimer: fluorescence enhancement after gelation

By coupling the features of anthracene and urea, a new low-molecular-weight gelator (LMWG, 1) with anthracene and urea moieties was designed and synthesized. A nontransparent gel of LMWG 1 in 1,2-dichloroethane was formed and characterized. Of particular interest is the observation of significant fluorescence enhancement after gelation, which is referred as to gelation-induced enhanced fluorescence emission. UV light irradiation of the THF solution of LMWG 1 yielded a photodimer with the h-t conformation. The photodimer can gel several organic solvents, including cyclohexane, n-hexane, and n-heptane. It should be mentioned that the gel based on the photodimer is rather stable. Our studies indicate that neither the gel phase based on LMWG 1 nor that based on the photodimer can be transformed to the solution by respective UV light irradiation or visible light irradiation/heating.     

Photosensitized cyclodimerizations of 4-vinylpyridine, 2-vinylpyridine,and 2-vinylquinoline

Irradiations of 4-vinylpyridine and of 2-vinylpyridine in either f-butyl alcohol or benzene, with benzophenone, yielded a single photodimer, which, on the basis of the nmr and mass spectral data, was assigned the trans-head-to-head structure (I). Upon irradiation in either t-butyl alcohol or benzene, in the presence of benzophenone, 2-vinylquinoline gave a single photodimer whose structure and stereochemistry were also determined from the nmr and mass spectral evidence as (V). Irradiation of 2-vinylquinoline in benzene, in the absence of benzophenone, also gave rise to the same photodimer, but, when t-butyl alcohol or methanol was used as a solvent, no dimer formation was observed.     

Template-assisted preferential formation of a syn photodimer in a pyrophosphate-induced self-assembly of a thymine-functionalized isothiouronium receptor

[reaction: see text] The effect of anion templation is investigated for the photodimerization of a thymine-functionalized isothiouronium receptor. The receptor forms a photodimer at the thymine moiety in methanol upon UV irradiation, while the isothiouronium moiety works as an oxoanion binding site via a two-point hydrogen-bonding motif. As compared to the case of a free receptor, the presence of pyrophosphate (PPi) resulted in the preferential formation of the syn-type photodimer, which would be desirable for recognizing the templated PPi.     

Functional monomers and polymers 159 synthesis and photochemical reactions of polymers containing thymine photodimer units in the main chain

Polyamides containing thymine photodimer units in the main chain were synthesized, and their photolysis by ultraviolet irradiation below 260 nm were studied in film state. Photodimers of thymine derivatives were obtained by photochemical reaction of the carboxylic acid derivatives of thymine in aqueous solution irradiated above 270 nm. An attempt was made to resolve the isomers of the photodimers, and the two kinds of cis isomers [cis–syn(head to head), and cis–anti(head to tail)] were isolated successfully. The polyamides were prepared by condensation of the photodimers with diamine using an activated ester method. The photodissociation of the thymine photodimer in the polymer main chain caused the breakage of the polymer chains, leading to the production of oligomers and dimer compounds containing thymine bases at the ends of the molecule. The dissociation rate of the polymer did not depend on the kind of the thymine photodimer which was in the main chain of the polymer.     

Self-assembling bisurea macrocycles used as an organic zeolite for a highly stereoselective photodimerization of 2-cyclohexenone

We report a highly selective 2 + 2 cycloaddition of 2-cyclohexenone in the presence of self-assembled bisurea macrocycles that yields the head-to-tail photodimer. The reaction proceeds with high conversion and with decreased incidence of secondary photorearrangement. Furthermore, the product can be extracted from the assembly, and the solid assembly is readily recovered and reused, much like a zeolite.