Role of cations and confinement in asymmetric photochemistry: enantio- and diastereo-selective photocyclization of tropolone derivatives within zeolites
Role of cations and confinement in asymmetric photochemistry: enantio- and diastereo-selective photocyclization of tropolone derivatives within zeolites
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DOI：
10.1039/b504865f
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发表时间：
2005-01-01
影响因子：
3.2
通讯作者：
Ramamurthy, V
中科院分区：
文献类型：
--
作者：
Joy, A;Kaanumalle, LS;Ramamurthy, V
使用托酚酮的光化学作为模型探索了光化学反应中的不对称诱导。已经研究了三种方法：手性感应器、手性辅助和[手性感应器+手性辅助]。所有三种方法在沸石中都给出了优异的不对称感应，而在溶液中则给出了非常小的或零感应。关于托酚酮的结果清楚地说明了充满阳离子的确定空间对不对称诱导的显着影响。托酚酮衍生物在照射后经历4个π电子电环化，产生双环产物和重排产物。环化产物的对映体过量率高达 68%。在手性诱导剂共价连接的系统中，沸石内的非对映异构体过量率高达 88%，而溶液中的同一系统则为 10%。
Asymmetric induction in photochemical reactions has been explored using the photochemistry of tropolones as a model. Three approaches have been examined: chiral inductor, chiral auxiliary and [chiral inductor + chiral auxiliary]. All three methods gave excellent asymmetric induction in zeolite and very little or zero induction in solution. Results presented on tropolones clearly illustrate the remarkable influence that a confirmed space studded with cations can have on asymmetric induction. Tropolone derivatives, upon irradiation undergo 4 pi-electron electrocyclization to yield a bicyclic product and a rearranged product. Enantiomeric excess up to 68% has been achieved in the cyclized product. In systems where a chiral inductor has been covalently linked, diastereomeric excess as high as 88% has been achieved within a zeolite while the same system in solution gave 10%.