Paper
Silver-mediated cycloaddition of alkynes with CF3CHN2: highly regioselective synthesis of 3-trifluoromethylpyrazoles.
Published Jun 10, 2013 · Feng Li, J. Nie, Long Sun
Angewandte Chemie
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Abstract
immense usefulness of 3-trifluoromethylpyrazole derivatives, efficient construction of the 3-trifluoromethylpyrazole framework has become the subject of intensive research in the fields of synthetic and medicinal chemistry. Generally, 3-trifluoromethylpyrazoles can be accessed by cyclocondensations of an appropriate hydrazine with the corresponding 1,3-dicarbonyl compounds. However, these methods often suffer from the formation of regioisomeric mixtures with respect to substituents incorporated at the 3and 5-positions of the pyrazole ring. Recently, 2,2,2-trifluorodiazoethane has emerged as an attractive synthon in transition-metal-catalyzed/mediated and organocatalytic reactions for the construction of fluorinecontaining building blocks. In this regard, Morandi, Carreira, and co-workers disclosed a rhodium-catalyzed cyclopropenation of alkynes with CF3CHN2 generated in situ from CF3CH2NH2·HCl in aqueous media, [6b] and we developed the copper(I)-catalyzed cross-coupling of terminal alkynes and gaseous CF3CHN2, thus leading to the formation of C H insertion products (Scheme 1, top). These reactions
Highly CitedSilver-mediated cycloaddition of alkynes with CF3CHN2 provides a highly regioselective synthesis of 3-trifluoromethylpyrazoles, offering potential for synthetic and medicinal chemistry applications.
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