Pyrazole-4-carbaldehyde synthesis

Synthesis The pyrazole-4-carbaldehyde synthesized according to Vilsmeier is reduced to the alcohol, which is chlorinated. The chloro derivative is reacted with sodium cyanide to give the nitrile, which is hydrolyzed to Lonazolac. The calcium salt, slightly soluble in water, is formed by adding calcium chloride to the free acid (Rainer et al., 1981 Unterhalt, 1982 Rainer et al. (Byk Gulden), 1969 1982 Kleemann et al., 1999). 

There are only a few reports in this area. Reaction of a pyrazolyl disulfide 377 with bromotrifluoromethane and ethyl bromide in the presence of sodium dithionite at room temperature afforded pyrazolyl sulfides 378. Oxidation of these with hydrogen peroxide in trifluoroacetic acid afforded sulfenylpyrazoles 379 in excellent yields (Scheme 41) <2006JFC(127)948>. Pyrazole-4-carbaldehyde 380 has been utilized in the efficient synthesis of... 

Pyrazole and fused heterocychc systems such as dipyrazolo[3,4-l> 3 4 -material chemistry. Sackus, Holzer, and coworkers have developed a new copper-free tandem cycHzation for the synthesis of pyrazolo[4, 3h3,4]pyr-ido[l,2-ii]perimidine 71 from 5-alkynylpyrazole-4-carbaldehydes 69 and 8-naphthalenediamine 70 (2015T(71)3385). They have found that conventional heating of the 5-aIkynylpyrazole-4-carbaldehydes 69 with... 

A simple protocol for synthesis of a series of l-(4-substituted phenyl)-3-phe-nyl-lH-pyrazole-4-carbaldehyde has been developed under microwave irradiation (Selvam et al., 2011). 

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