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Cu‐Promoted Sydnone Cycloadditions of Alkynes: Scope and Mechanism Studies
Author(s) -
ComasBarceló Júlia,
Foster Robert S.,
Fiser Béla,
GomezBengoa Enrique,
Harrity Joseph P. A.
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201406118
Subject(s) - sydnone , cycloaddition , chemistry , reaction mechanism , mechanism (biology) , medicinal chemistry , combinatorial chemistry , catalysis , organic chemistry , ring (chemistry) , philosophy , epistemology
Cu salts have been found to promote the cycloaddition reaction of sydnones and terminal alkynes, providing significant reduction in reaction times. Specifically, the use of Cu(OTf) 2 is found to provide 1,3‐disubstituted pyrazoles, whereas simply switching the promoter system to Cu(OAc) 2 allows the corresponding 1,4‐isomers to be produced. The mechanism of the Cu‐effect in each case has been investigated by experimental and theoretical studies, and they suggest that Cu(OTf) 2 functions by Lewis acid activation of the sydnone, whereas Cu(OAc) 2 promotes formation of reactive Cu I acetylides.