A range of pyrazol-5-one and pyrazol-3-one derivatives has been synthesized in a single step via a palladium-catalyzed carbonylation of aromatic or aliphatic α-chloroketones, in the presence of aromatic or aliphatic hydrazines. A reaction mechanism, explaining the observed regioselectivity, has been also discussed.
Enantioselective Synthesis of Functionalized Pyrazoles by NHC-Catalyzed Reaction of Pyrazolones with α,β-Unsaturated Aldehydes
作者:Santhivardhana Reddy Yetra、Santigopal Mondal、Eringathodi Suresh、Akkattu T. Biju
DOI:10.1021/acs.orglett.5b00293
日期:2015.3.20
The N-heterocyclic carbene (NHC)-organocatalyzed enantioselectiveannulation reaction of pyrazolones with α,β-unsaturated aldehydes proceeding via the chiral α,β-unsaturatedacylazolium intermediates under oxidative conditions is presented. The reaction afforded dihydropyranone-fused pyrazoles in moderate to good yields and good er values under operationally simple and base-free conditions.