Categories: Synthesis of N-Heterocycles >
Synthesis of 3H-pyrazoles
Recent Literature
FeCl3 mediates a propargylic substitution of tertiary propargylic
alcohols with p-toluenesulfonyl hydrazide. A subsequent cyclization under
mild conditions in the presence of iodine enables an efficient and rapid
synthesis of iodo-3H-pyrazoles with a wide substrate scope and in high
yields.
X.-T. Liu, Z.-C. Ding, L-C. Ju, Z.-N. Tang, F. Wu, Z.-P. Zhan,
Synlett, 2017, 28, 620-624.
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.
Q. Sha, Y. Wei, Synthesis, 2013, 45, 413-420.