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Formyl Substituent at C‐4 of Pyrazoles: A Temporary Protecting Group for Regioselective Palladium‐Catalyzed Direct Arylation at C‐5
Author(s) -
Smari Imen,
Youssef Chiraz,
Yuan Kedong,
Beladhria Anissa,
Ben Ammar Hamed,
Ben Hassine Bechir,
Doucet Henri
Publication year - 2014
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.201301593
Subject(s) - regioselectivity , aldehyde , substituent , chemistry , palladium , aryl , pyrazole , hydrazine (antidepressant) , catalysis , dimethylformamide , medicinal chemistry , organic chemistry , combinatorial chemistry , alkyl , chromatography , solvent
Pyrazoles with an aldehyde function at C‐4 underwent a palladium‐catalyzed direct arylation reaction to provide a regioselective approach to 5‐aryl‐substituted pyrazoles. The reaction proceeds in moderate to high yields with a variety of aryl bromides in the presence of 2 mol‐% of Pd(OAc) 2 as the catalyst. The use of an aldehyde function at C‐4 of the pyrazoles presents several advantages: (1) 4‐formylpyrazoles are easily prepared from hydrazine derivatives, ketones, and N , N ‐dimethylformamide (DMF), (2) the control of the regioselectivity of the arylation at C‐5 of the pyrazole, (3) the aldehyde substituent can easily be transformed into a wide variety of other substituents, and (4) the formyl group can be considered a temporary protecting group, as it can be removed by a straightforward reaction.