Rare‐Earth Catalyzed C−H Bond Alumination of Terminal Alkynes
Rare‐Earth Catalyzed C−H Bond Alumination of Terminal Alkynes
复制标题
稀土催化末端炔烃C-H键铝化反应
DOI：
10.1002/chem.202000325
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Sadow, Aaron D.
中科院分区：
文献类型：
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作者：
Kanbur, Uddhav;Sadow, Aaron D.
有机铝试剂在催化C-H键官能化中的应用受到竞争性副反应的限制，如碳铝化和铝氢化。在本文中，稀土四甲基铝酸盐络合物被证明可以催化末端炔与商品试剂三甲基-，三乙基-和三异丁基铝的排他性C-H键金属化。探索稀土铝酸盐和三烷基铝之间的烷基交换、炔的C-H键金属化和催化转化的动力学实验揭示了三乙基铝与三甲基铝催化铝化的不同途径。最重要的是，动力学数据表明可逆形成独特的[Ln]（AlR 4）2-AlR 3加合物，然后是限制周转的炔金属化。也就是说，C-H键活化发生在更相关的有机金属物种，而不是预期的配位不饱和物种。这些机理结论暗示了催化C-H键铝化的新通用策略，该策略利用高度亲电金属催化剂。
Organoaluminum reagents’ application in catalytic C−H bond functionalization is limited by competitive side reactions, such as carboalumination and hydroalumination. Herein, rare‐earth tetramethylaluminate complexes are shown to catalyze the exclusive C−H bond metalation of terminal alkynes with the commodity reagents trimethyl‐, triethyl‐, and triisobutylaluminum. Kinetic experiments probing alkyl‐group exchange between rare‐earth aluminates and trialkylaluminum, C−H bond metalation of alkynes, and catalytic conversions reveal distinct pathways of catalytic aluminations with triethylaluminum versus trimethylaluminum. Most significantly, kinetic data point to reversible formation of a unique [Ln](AlR4)2⋅AlR3adduct, followed by turnover‐limiting alkyne metalation. That is, C−H bond activation occurs from a more associated organometallic species, rather than the expected coordinatively unsaturated species. These mechanistic conclusions allude to a new general strategy for catalytic C−H bond alumination that make use of highly electrophilic metal catalysts.