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DMF‐Catalyzed Direct and Regioselective C–H Functionalization: Electrophilic/Nucleophilic 4‐Halogenation of 3‐Oxypyrazoles
Author(s) -
Liu Yuanyuan,
He Guangke,
Chen Kai,
Jin Yin,
Li Yufeng,
Zhu Hongjun
Publication year - 2011
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.201100571
Subject(s) - halogenation , chemistry , regioselectivity , nucleophile , electrophile , thionyl chloride , catalysis , medicinal chemistry , dimethylformamide , organic chemistry , chloride , solvent
A novel, straightforward, and highly regioselective 4‐chlorination of 3‐oxypyrazole derivatives in boiling thionyl chloride (SOCl 2 ) in the presence of catalytic N , N ‐dimethylformamide (DMF) has been developed. This reaction likely proceeds through a DMF‐catalyzed electrophilic/nucleophilic chlorination mechanism and involves electrophilic attack by SOCl 2 and nucleophilic substitution by Cl – as the key steps. Based on this mechanism, the corresponding 4‐bromination and 4‐iodination of 3‐oxypyrazoles have also been achieved in good yield by adding Br – and I – , respectively, to the reaction system. This halogenation method enables quick access to many original 4‐halo‐3‐oxypyrazole series.