Reaction of 5‐aminopyrazole derivatives with ethoxymethylene‐malononitrile and its analogues

Abstract

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.

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

“…Reactions were carried out in ethanol or without a solvent. If the ratio enol ether/hydrazine is 1:1, as in the case of the reaction with 3c , the formation of 7-aminopyrazolo[1,5- a ]pyrimidine-3,6-dicarbonitrile could be expected as a byproduct [ 24 – 25 ]. When hydrazine hydrochloride is used [ 14 ], ethyl 3-ethoxypyrazole-4-carboxylate was obtained in 41% yield and the expected ethyl 3-oxo-2,3-dihydropyrazole-4-carboxylate ( 5c , oxo form) in 37% yield.…”

4-Quinolone Derivatives: High-Affinity Ligands at the Benzodiazepine Site of Brain GABAA Receptors. Synthesis, Pharmacology, and Pharmacophore Modeling

“…The pyrazolopyrimidinones were synthesized according to previously described procedures, utilizing a one-pot procedure which includes the condensation of 3-aminopyrazole and ethoxymethylenemalonate followed by cyclization of the intermediate. The alkyl chain was subsequently varied, by transesterification with n -propanol using titanium(IV) isopropoxide as a catalyst (Scheme ).…”

EMCA and DEEM as Michael Reagents Used in Organic Synthesis

“…26). Unsubstituted or 4-alkylsubstituted 3-aminopyrazoles reacted with DEEM in acetic acid [142][143][144] giving 7-oxopyrazolo[1,5-a]pyrimidine-6-carboxylates (28) (Fig. 27), the adenosine cyclic 3',5'-phosphate phosphodiesterase inhibitors [142].…”