A Bio-Inspired, Catalytic E → Z Isomerization of Activated Olefins
A Bio-Inspired, Catalytic E → Z Isomerization of Activated Olefins
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DOI：
10.1021/jacs.5b07136
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发表时间：
2015-09-09
影响因子：
15
通讯作者：
Gilmour, Ryan
中科院分区：
文献类型：
--
作者：
Metternich, Jan B.;Gilmour, Ryan
在这里，自然黄素介导的复合（多）烯的活化已被翻译成一个小分子范例，最终在(-)-核糖黄素活化烯烃的高度(Z)选择性催化异构化（高达99:1 Z/E）。与自然系统中突出的Z -> - E异构化相反，可以通过同时截断视网膜支架并引入第三个烯烃取代基来增强异构化时的A1,3-strain来逆转异构化（E -> - Z）的方向性。因此，产物发色团中的共轭作用减少，导致具有离散光物理特征的衬底/产物组合。操作简单的异构化方案已应用于各种烯酮衍生底物，并在制备医学相关的4-取代香豆素支架中展示。敏化剂三重态能（ET）与反应效率的相关性，加上加性效应和机理探针的研究，与三重态能量传递机制相一致。
Herein, Nature's flavin-mediated activation of complex (poly)enes has been translated to a small molecule paradigm culminating in a highly (Z)-selective, catalytic isomerization of activated olefins using (-)-ribo-flavin (up to 99:1 Z/E). In contrast to the prominent Z -> E isomerization of the natural system, it was possible to invert the directionality of the isomerization (E -> Z) by simultaneously truncating the retinal scaffold, and introducing a third olefin substituent to augment A1,3-strain upon isomerization. Consequently, conjugation is reduced in the product chromophore leading to a substrate/product combination with discrete photophysical signatures. The operationally simple isomerization protocol has been applied to a variety of enone-derived substrates and showcased in the preparation of the medically relevant 4-substituted coumarin scaffold. A correlation of sensitizer triplet energy (ET) and reaction efficiency, together with the study of additive effects and mechanistic probes, is consistent with a triplet energy transfer mechanism.