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A one‐pot synthesis using 5‐aminopyrazole derivatives 1 with ethoxymethylenemalononitrile (EMMN), ethyl ethoxymethylenecyanoacetate (EMCA) or diethyl ethoxymethylenemalonate (DEMM) gave pyrazolo‐[1,5‐a]pyrimidine compounds 2,4,8. Also, the one step reaction of EMCA with hydrazine hydrate afforded ethyl(4‐ethoxycarbonyl‐5‐pyrazolyl)aminomethylenecyanoacetate 3c. On the other hand, the reaction of 1‐substituted 5‐aminopyrazole‐4‐carboxamide 9 with EMMN afforded pyrazolo[3,4‐d]pyrimidine compounds 10.
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Nagahara et al. (1994) studied this question.
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