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
Qiang Sha, Yunyang Wei*
*School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. of China, Email: yweimail.njust.edu.cn
Q. Sha, Y. Wei, Synthesis, 2013, 45, 413-420.
A simple, highly efficient, 1,3-dipolar cycloaddition of diazo compounds and alkynyl bromides gives 3,5-diaryl-4-bromo-3H-pyrazoles or the isomerization products 3,5-diaryl-4-bromo-1H-pyrazoles in good yields. The diazo compounds and alkynyl bromides were generated in situ from tosylhydrazones and gem-dibromoalkenes, respectively. The reaction system exhibited high regioselectivity and good functional group tolerance.
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