- Pyrazolopyrimidines based on 5-aminopyrazoles unsubstituted at the position 1
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By condensation of various symmetric β-diketones with a series of 5-aminopyrazoles that are unsubstituted at the position 1, we have obtained a series of pyrazolo[1,5-a]pyrimidines that are of interest as physiologically active compounds. Hexafluoroacetylacetone reacts in another direction, forming pyrazolo[4,5-b]pyridine.
- Nam,Grandberg,Sorokin
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- Reactivity of electrogenerated thiocyanogen in the thiocyanation of pyrazolo[1,5-a]pyrimidines
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Selective thiocyanation (yield 70–90%) at the 3-position of pyrazolo[1,5-a]pyrimidines was performed with thiocyanogen electrochemically generated in situ from NH4SCN in MeCN on a Pt anode. For substrates with higher oxidation potential addition of Lewis acids was necessary.
- Kokorekin, Vladimir A.,Yaubasarova, Rauza R.,Neverov, Sergei V.,Petrosyan, Vladimir A.
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- Convenient synthesis of substituted 3-alkenylpyrazolo[1,5-a]pyrimidines via Heck cross-coupling reaction
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3-Iodopyrazolo[1,5-a]pyrimidines 3 were easily obtained by direct iodination of pyrazolo[1,5-a]pyrimidines 2 with NIS and could be transformed into a series of new substituted 3-alkenyl-pyrazolo[1,5-a]pyrimidines 5 by Heck cross-coupling.
- Yin, Lunxiang,Liebscher, Juergen
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p. 2329 - 2334
(2007/10/03)
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- Chemical and Electrochemical Reduction of some Pyrazolopyrimidines
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Various pyrazolopyrimidines 1 are prepared by two different ways.Their chemical reduction by sodium borohydride leads generally to 4,5,6,7-tetrahydro compounds 3, while lithium aluminum hydride yields 4,7-dihydro derivatives 2 at room temperature, and 3 in refluxing tetrahydrofuran.A complex mixture of oxidizable hydrodimers is obtained by electrochemical reduction.An electroreduction at a more negative potential also gives 4,7-dihydro compounds 2.A new 4,5-dihydropyrazolopyrimidine has been obtained by condensation of 5-amino-3-methyl-1H-pyrazole with acetophenone.
- Bellec, Christian,Lhommet, Gerard
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p. 1793 - 1800
(2007/10/03)
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