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-1<b>H</b>-pyrazole-5-carboxylates as stable intermediates in the pyrazole ring formation
作者:Andrej Hanzlowsky、Blanka Jelenčič、Simon Rečnik、Jurij Svete、Amalija Golobič、Branko Stanovnik
DOI:10.1002/jhet.5570400313
日期:2003.5
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 (51) 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
3-[(E)-(二甲基氨基)亚甲基]丙酮酸乙酯(3)和3-[(二甲基氨基)亚甲基] -2-氧代琥珀酸酯(4)与肼一盐酸盐(5a)和(杂)芳基肼(5b)的反应-i)区域选择性地分别提供1-取代的1 H-吡唑-5-羧酸乙酯9a-f和二乙基1 H-吡唑-3,4-二羧酸乙酯11a-i。用哒嗪基肼5d-f处理3时,稳定的中间体1-取代的4,5-二氢-5-羟基-1 H-吡唑-5-羧酸乙酯8d-f,被隔离。在乙酸中在回流下处理化合物8d-f,得到吡唑9d-f。另一方面,使3与N,N′-二甲基肼(51)反应,得到1-甲基-1H-吡唑-3-羧酸乙酯(14)。化合物的结构3,4,14通过NMR(NOESY和HMBC技术)确定,而化合物的结构8F,9F,和11E,F,用X射线衍射测定。