Copper(I) Acetate‐Catalyzed Cycloaddition between Azomethine Imines and Propiolates under Additive‐Free Conditions
Copper(I) Acetate‐Catalyzed Cycloaddition between Azomethine Imines and Propiolates under Additive‐Free Conditions
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DOI：
10.1002/ejoc.201300753
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发表时间：
2013-10
影响因子：
2.8
通讯作者：
C. Shao;Qun-Liang Zhang;Guolin Cheng;Chuanjie Cheng;Xinyan Wang-;Yuefei Hu
中科院分区：
文献类型：
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作者：
C. Shao;Qun-Liang Zhang;Guolin Cheng;Chuanjie Cheng;Xinyan Wang-;Yuefei Hu
由于丙醇酸盐很容易发生碱催化的自迈克尔加成反应，CuAAC中大多数常用的催化体系不能用于甲亚胺和丙醇酸盐之间的环加成反应，因为此类反应通常需要使用叔胺作为添加剂(作为碱和/或配体)。我们发现，这个问题可以简单地用乙酸铜作为催化剂来解决，在催化剂中，乙酸铜作为配体，在反应过程中转化为醋酸。因此，乙酸铜催化的环加成反应实际上是在无添加剂(没有外源配体)的条件下进行的，从而有效地合成了6，7-二氢吡唑并[1，2-a]吡唑酮衍生物，完全避免了碱性添加剂引起的副反应和副产物。
Because propiolates easily undergo base-catalyzed self-Michael addition, most popular catalytic systems in CuAAC cannot be used in the cycloaddition between azomethine imines and propiolates, because such reactions usually require the use of tertiary amines as additives (as base and/or ligand). We found that this problem can be resolved simply by using copper(I) acetate as catalyst, in which the acetate serves as a ligand and is converted into acetic acid during the reaction. Thus, copper(I) acetate catalyzed cycloaddition actually proceeds under additive-free conditions (without exogenous ligand) to efficiently give 6,7-dihydropyrazolo[1,2-a]pyrazolone derivatives, in which the side-reactions and byproducts caused by basic additives are completely avoided.