Fujioka H, Yasui M, Hamada S, Fukumi K, Takeda N, Kobayashi Y, Furuta T, Ueda M. Palladium-catalyzed C-C bond cleavage of
N-cyclopropyl acylhydrazones.
Org Biomol Chem 2024;
22:3262-3267. [PMID:
38568183 DOI:
10.1039/d4ob00349g]
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Abstract
Despite their utility as directing groups, the C-C bond cleavage of cyclopropanes utilizing hydrazones has not been explored. Herein, Pd-catalyzed C-C bond cleavage reaction of N-cyclopropyl acylhydrazones, followed by cycloisomerization to yield pyrazoles, has been developed. The protocol enables the synthesis of various α-pyrazole carbonyl compounds, which have a potential of biological activity. Control experiments and DFT calculations suggest that β-carbon elimination of a stable 6-membered chelate palladium complex occurs, generating a conjugated azine as a reaction intermediate for the following cycloisomerization.
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