Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst.
Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst.
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DOI：
10.3762/bjoc.11.211
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发表时间：
2015
影响因子：
2.7
通讯作者：
Vincent JM
中科院分区：
文献类型：
--
作者：
Beniazza R;Bayo N;Molton F;Duboc C;Massip S;McClenaghan N;Lastécouères D;Vincent JM
寻找能够在没有抗坏血酸钠的情况下在水中有效进行点击反应的铜催化剂是当前研究的一个活跃领域，在生物共轭方面具有巨大的应用潜力。水溶性、光还原性铜(II)-EDA（EDA = 乙二胺）络合物 1 具有两个 4-苯甲酰基苯甲酸酯，既充当抗衡离子又充当光敏剂，已通过包括单晶 X 射线衍射在内的不同技术进行了合成和表征。当 1 的氢原子供给溶剂（例如 THF 或 MeOH）溶液暴露于由低压汞灯（TLC 型 = 薄层色谱，365 nm）、23 W 荧光灯或环境光/阳光提供的 UVA 辐射（350–400 nm）时，可实现高效光还原。在水中这种氢原子供给性较差的溶剂中，1的光还原被证明是低效的。有趣的是，EPR 研究表明，当溶液中存在炔烃时，配合物 1 仍然可以在水中被有效光还原。在各种光照条件下测试了 1 对涉及一系列水溶性炔烃和叠氮化物，特别是糖类的点击反应的催化活性。配合物 1 被发现表现出光潜特性，光生铜 (I) 具有很强的反应性。在 365 nm（TLC 灯）下照射含有 1 mol% 1 的水性反应混合物 1 小时后，点击反应显示出完全转化。
The search for copper catalysts able to perform effectively click reactions in water in the absence of sodium ascorbate is an active area of current research with strong potential for applications in bioconjugation. The water-soluble and photoreducible copper(II)–EDA (EDA = ethylenediamine) complex 1, which has two 4-benzoylbenzoates acting as both counterion and photosensitizer, has been synthesized and characterized by different techniques including single crystal X-ray diffraction. Highly efficient photoreduction was demonstrated when solutions of 1 in hydrogen atom donating solvents, such as THF or MeOH, were exposed to UVA radiation (350–400 nm) provided by a low pressure mercury lamp (type TLC = thin-layer chromatography, 365 nm), or by a 23 W fluorescent bulb, or by ambient/sunlight. In water, a much poorer hydrogen atom donating solvent, the photoreduction of 1 proved inefficient. Interestingly, EPR studies revealed that complex 1 could nonetheless be effectively photoreduced in water when alkynes were present in solution. The catalytic activity of 1 for click reactions involving a range of water-soluble alkynes and azides, in particular saccharides, was tested under various illumination conditions. Complex 1 was found to exhibit a photolatent character, the photogenerated copper(I) being very reactive. On irradiating aqueous reaction mixtures containing 1 mol % of 1 at 365 nm (TLC lamp) for 1 h, click reactions were shown to proceed to full conversion.