ORGANIZED PHOTODIMERIZATION OF UNSATURATED CARBOXYLATES. SELECTIVITY CONTROL BY NORMAL AND REVERSED MICELLES
ORGANIZED PHOTODIMERIZATION OF UNSATURATED CARBOXYLATES. SELECTIVITY CONTROL BY NORMAL AND REVERSED MICELLES
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不饱和羧酸盐的有组织光二聚。
DOI：
10.1039/p29940001003
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Y. Sawaki
中科院分区：
文献类型：
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作者：
K. Takagi;M. Itoh;H. Usami;T. Imae;Y. Sawaki
芳香族不饱和羧酸盐如肉桂酸盐和2-茚羧酸盐在长链烷基铵离子存在下，在水中形成聚集数为103数量级的短棒状胶束，在四氯化碳中形成包含2-3个表面活性剂分子的预胶束聚集体。结果发现，这些聚集体进行有效的和立体选择性的光二聚。在棒状胶束水溶液中的光反应导致主要形成的反头对头二聚体（抗HH），而在小聚集的预胶束中的反应产生了最不稳定的同步头对头二聚体（同步HH）。向预胶束聚集体中加入少量甲醇使主要产物从顺式HH转变为反式HH。对照实验表明，相应的甲酯的光反应提供了四个异构体二聚体，顺式和反HH和HT（头到尾），统计分布的混合物。这些立体化学的选择性进行了讨论，在有组织的烯烃取向和相关的光散射和NMR探针技术的结果。
Aromatic unsaturated carboxylates such as cinnamate and 2-indenecarboxylate form, in the presence of long-chain alkylammonium ion, short rod-like micelles with an aggregation number of an order of 103 in water and premicelle aggregates including 2–3 surfactant molecules in carbon tetrachloride. It was found that these aggregates undergo efficient and stereoselective photodimerizations. Photoreactions in aqueous rod-like micellar solutions resulted in the predominant formation of anti-head-to-head dimers (anti-HH), while the reaction in small aggregated premicelles yielded thermodynamically least stable syn-head-to-head dimers (syn-HH). The addition of a small amount of methanol to the premicelle aggregate shifted the major product from syn-HH to anti-HH. Control experiments showed that the photoreaction of the corresponding methyl ester afforded mixtures of four isomeric dimers, syn- and anti-HH and HT (head-to-tail), of statistical distribution. These stereochemical selectivities are discussed in terms of the organized olefin orientation and correlated to the results of light scattering and NMR probe techniques.