An Efficient One-Pot Synthesis of 3,5-Diaryl-4-bromopyrazoles by 1,3-Dipolar Cycloaddition of In Situ Generated Diazo Compounds and 1-Bromoalk-1-ynes

A simple, highly efficient, one-pot synthesis of 3,5-diaryl-4-bromopyrazoles via 1,3-dipolar cycloaddition of diazo compounds and alkynyl bromides has been developed. The diazo compounds and alkynyl bromides were generated in situ from tosylhydrazones and gem-dibromoalkenes, respectively. When keton...

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Bibliographic Details
Published inSynthesis (Stuttgart) Vol. 45; no. 3; pp. 413 - 420
Main Authors Sha, Qiang, Wei, Yunyang
Format Journal Article
LanguageEnglish
Published STUTTGART Thieme Medical Publishers 01.02.2013
Subjects
Chemistry
Chemistry, Organic
Physical Sciences
Science & Technology
ORGANIC-SYNTHESIS
ARYLATION
CYCLOPROPENE
gem-dibromoalkenes
C-13 MAGNETIC-RESONANCE
cycloaddition
ELECTRONIC EXCITED-STATES
VINYLCARBENE
pyrazoles
diazo compounds
TAUTOMERISM
DERIVATIVES
hydrazones
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Summary:A simple, highly efficient, one-pot synthesis of 3,5-diaryl-4-bromopyrazoles via 1,3-dipolar cycloaddition of diazo compounds and alkynyl bromides has been developed. The diazo compounds and alkynyl bromides were generated in situ from tosylhydrazones and gem-dibromoalkenes, respectively. When ketone-derived hydrazones were used, 3,5-diaryl-4-bromo-3H-pyrazoles were obtained and the isomerization products 3,5-diaryl-4-bromo-1H-pyrazoles were formed when using aldehyde-derived hydrazones. The reaction system exhibited high regioselectivity and good functional group tolerance. Both electron-rich and electron-deficient substituents on the aromatic ring of the hydrazones or the gem-dibromoalkenes gave desired products in moderate to good yields (67-86%).
ISSN:0039-7881
1437-210X
DOI:10.1055/s-0032-1317992