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Copper(I) Acetate‐Catalyzed Cycloaddition between Azomethine Imines and Propiolates under Additive‐Free Conditions
Author(s) -
Shao Changwei,
Zhang Qun,
Cheng Guolin,
Cheng Chuanjie,
Wang Xinyan,
Hu Yuefei
Publication year - 2013
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201300753
Subject(s) - chemistry , cycloaddition , catalysis , ligand (biochemistry) , acetic acid , copper , combinatorial chemistry , base (topology) , organic chemistry , receptor , mathematical analysis , biochemistry , mathematics
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.