16078-69-6Relevant academic research and scientific papers
Regioselective synthesis of ethyl pyrazolecarboxylates from ethyl 3-[(dimethylamino)methylidene]pyruvate and diethyl 3-[(dimethylamino)methylidene]-2-oxosuccinate. Isolation of ethyl 4,5-dihydro-1-heteroaryl-5-hydroxy-1H-pyrazole-5-carboxylates as stable intermediates in the pyrazole ring formation
Hanzlowsky, Andrej,Jelencic, Blanka,Recnik, Simon,Svete, Jurij,Golobic, Amalija,Stanovnik, Branko
, p. 487 - 498 (2007/10/03)
Reactions of ethyl 3-[(E)-(dimethylamino)methylidene]pyruvate (3) and 3-[(dimethylamino)methylidene]-2-oxosuccinate (4) with hydrazine monohydrochloride (5a) and (hetero)arylhydrazines (5b-i) afforded, regioselectively, 1-substituted ethyl 1H-pyrazole-5-carboxylates 9a-f and diethyl 1H-pyrazole-3,4-dicarboxylates, 11a-i, respectively. Upon treatment of 3 with pyridazinylhydrazines 5d-f, the stable intermediates, 1-substituted ethyl 4,5-dihydro-5-hydroxy-1H-pyrazole-5-carboxylates 8d-f, were isolated. Treatment of compounds 8d-f in acetic acid under reflux furnished the pyrazoles 9d-f. On the other hand, reaction of 3 with N,N′-dimethylhydrazine (5I) gave ethyl 1-methyl-1H-pyrazole-3-carboxylate (14). The structures of compounds 3, 4, 14 were determined by nmr (noesy and hmbc techniques), while the structures of compounds 8f, 9f, and 11e,f were determined by X-ray diffraction.
