- Rhodium-Catalyzed [4+2] Annulation of N-Aryl Pyrazolones with Diazo Compounds To Access Pyrazolone-Fused Cinnolines
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An efficient synthesis of novel dinitrogen-fused heterocycles such as pyrazolo[1,2-a]cinnoline derivatives have been accomplished by the rhodium(III)-catalyzed reaction of N-arylpyrazol-5-ones with α-diazo compounds. This reaction proceeds through a cascade C?H activation/intramolecular cyclization with a broad substrate scope. Furthermore, this protocol is successfully extended to the unusual phosphorus-containing α-diazo compounds and cyclic diazo compounds as the cross-coupling partners to deliver the two new kinds of pyrazolo[1,2-a]cinnolinones. The control experiments were performed to reveal insight into the mechanism of this reaction, involving reversible C?H activation, migratory insertion of the diazo compound, and cascade cyclization as the key steps of the transformation. Moreover, gram-scale synthesis and further transformation of the target product demonstrate the synthetic utility of the present protocol.
- Dhole, Sandip,Huang, Wan-Wen,Huang, Ying-Ti,Lin, Chih-Yu,Sun, Chung-Ming
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supporting information
p. 4984 - 4992
(2021/09/28)
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- Tunable Aerobic Oxidative Hydroxylation/Dehydrogenative Homocoupling of Pyrazol-5-ones under Transition-Metal-Free Conditions
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A practical and tunable transition-metal-free aerobic oxidation of pyrazol-5-ones preparing either 4-hydroxypyrazoles (via C-H hydroxylation) or bispyrazoles (via dehydrogenative homocoupling) is described. The K2CO3/dioxane reagent system predominately promoted hydroxylation to deliver the α-hydroxylated pyrazoles. In contrast, the formation of bispyrazoles was overwhelmingly preferred with CH3CN as the reaction medium without any additives.
- Sheng, Xuguang,Zhang, Jinlong,Yang, Huameng,Jiang, Gaoxi
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supporting information
p. 2618 - 2621
(2017/05/24)
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- Catch-and-release of HNO with pyrazolones
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A new and versatile class of HNO donors, the (hydroxylamino)pyrazolone (HAPY) series of HNO donors utilizing pyrazolone (PY) leaving groups, is described. HNO, the smallest N-based aldehyde equivalent, is used as a reagent along with a variety of PY compounds to synthesize the desired HAPY donors in what can be considered an N-selective HNO-aldol reaction in up to quantitative yields. The bimolecular rate constant of HNO with PY in pH 7.4 phosphate buffer at 37 °C can reach 8 × 105 M-1 s-1. In 1H NMR experiments, the HAPY compounds generate HNO quantitatively (trapped as a phosphine aza-ylide) with half-lives spanning 3 orders of magnitude (minutes to days) under physiologically relevant conditions. B3LYP/6-31G calculations confirm the energetically favorable reactions between HNO and the PY enol and enolate, whereas HNO release is expected to occur through the oxyanion (OHN-PY) of each HAPY compound. HNO has been shown to provide functional support to failing hearts.
- Guthrie, Daryl A.,Ho, Anthony,Takahashi, Cyrus G.,Collins, Anthony,Morris, Matthew,Toscano, John P.
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p. 1338 - 1348
(2015/02/19)
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- Alkynylation of heterocyclic compounds using hypervalent iodine reagent
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The alkynylation of various nitrogen- and/or sulphur-containing heterocyclic compounds using hypervalent iodine TMS-EBX by utilization of tertiary amines under mild conditions is described. The developed metal-free methodology furnishes the corresponding alkynylated heterocycles bearing quaternary carbon in high yields.
- Kamlar,Císa?ová,Vesely
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supporting information
p. 2884 - 2889
(2015/04/27)
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- DRUGS COMPRISING COMBINATION OF ANTITHROMBOTIC AGENT WITH PYRAZOLONE DERIVATIVE
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It is intended to provide drugs for treating and/or preventing ischemic diseases which are safe and have little side effects. Namely, drugs comprising a combination of an antithrombotic agent and a pyrazolone derivative defined in the description or its pharmaceutically acceptable salt.
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- Solid-phase synthesis of substituted pyrazolones from polymer-bound β-keto esters
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Polymer-bound acetoacetate 3 was γ-mono- and γ-dialkylated, as well as α-monoalkylated, to give 6, 9, and 13, respectively. Treatment with hydrazine or substituted hydrazines followed by thermal or acidic cyclizing cleavage yielded the pyrazolones 17a-dd in a purity of >90%.
- Tietze, Lutz F.,Evers, Holger,Hippe, Thomas,Steinmetz, Adrian,T?pken, Enno
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p. 1631 - 1634
(2007/10/03)
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- Solid-phase synthesis of polymer-bound β-ketoesters and their application in the synthesis of structurally diverse pyrazolones
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An efficient solid-phase synthesis of different polymer-bound β-ketoesters 7 is described using readily available acid chlorides 1 and haloalkanes 6 as building blocks. The corresponding pyrazolones 9 and 10 were obtained by mild acid catalyzed reaction with phenylhydrazine or by treatment with hydrazine under cyclisation and cleavage from the resin in high purity and good yield.
- Tietze, Lutz F.,Steinmetz, Adrian,Balkenhohl, Friedhelm
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p. 1303 - 1306
(2007/10/03)
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