Acetylenylpyrazolecarboxylic Acids

Thus, the vic-acetylenylpyrazolecarboxylic acids are isomerized into pyranoa-zoles in boiling pyridine (20-30 min) with catalytic amounts of copper acetylide. The acetylide condensation of the corresponding iodopyrazolecarboxylic acids is followed by cyclization into the same 5-lactones but with a lower rate (2-8 h). 

In conditions of base catalysis, the acetylenylpyrazolecarboxylic acid hydrazides, as opposed to benzene derivatives, are more difficult to cyclize compared with the benzoic acid derivatives and are isomerized only after heating in alcohol in the presence of KOH, forming not five- but six-membered lactams. The yields of pyri-dopyrazoles were 80-90% (Scheme 133 Table XXVIII) (85IZV1367 85MI2). 

A simple cyclization of hydrazides of o-acetylenylbenzoic and acetylenylpyrazolecarboxylic acid 50 can lead to four different compounds, namely the five-membered A-aminolactams, six-membred iV-amino lactams, and six-mem-bered diazinones and diazepinones, but only the first three have been reported. The unexpected formation of bis(pyrazolo[4,3- 7][l,2]diazepinone 51 (R = 4-MeOC6H4) structure has been established by X-ray crystallography <2005TL4457> (Equation 4). 

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