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.
A novel one‐pot, three‐component diastereo‐ and enantioselective synthesis of spiropyrazolones has been developed involving the aldol condensation of an enal to generate α,β‐unsaturated pyrazolones, which react with a second equivalent of enal through an N‐heterocyclic carbene (NHC)‐catalyzed [3+2] annulation. The desired spirocyclopentane pyrazolones are obtained in moderate to good yields and good
Asymmetric Synthesis of Spiropyrazolones through Phosphine-Catalyzed [4+1] Annulation
作者:Xiaoyu Han、Weijun Yao、Tianli Wang、Yong Ren Tan、Ziyu Yan、Jacek Kwiatkowski、Yixin Lu
DOI:10.1002/anie.201311214
日期:2014.5.26
enantioselective synthesis of spiropyrazolones from allenoate‐derived MBH acetates and pyrazolones through a phosphine‐mediated [4+1] annulation process has been developed. Spiropyrazolones were readily prepared in good chemical yields and good to high enantioselectivities. This is the first asymmetric example in which α‐substituted allenoates were utilized as a C4 synthon for phosphine‐catalyzed [4+1] annulation