Synthesis of N-aminopyrazoles by Fe(II)-catalyzed rearrangement of 4-hydrazonomethyl-substituted isoxazoles
作者:Ekaterina E. Galenko、Viktor K. Ivanov、Mikhail S. Novikov、Andrey A. Zolotarev、Alexander F. Khlebnikov
DOI:10.1016/j.tet.2018.09.015
日期:2018.10
derivatives by Fe(II)-catalyzed rearrangement of isoxazoles having (2,4-dinitrophenylhydrazono)methyl substituent at C4. The reaction proceeds smoothly for both E and Z isomers of 4-(hydrazonomethyl)isoxazoles, and this means it is not necessary to separate mixtures of E/Z-isomers of the hydrazones prepared by reaction of 5-methoxy/pirrolidino-4-carbonylisoxazoles and 2,4-dinitrophenylhydrazine. The rearrangement
报道了一种新的有效方法,该方法通过Fe(II)催化在C4具有(2,4-二硝基苯基肼基)甲基取代基的异恶唑的重排制备1-氨基-1 H-吡唑-4-羧酸衍生物。对于4-(肼基甲基)异恶唑的E和Z异构体,反应均顺利进行,这意味着不必分离通过5-甲氧基/吡咯烷基--4-羰基异恶唑反应制得的的E / Z-异构体的混合物。和2,4-二硝基苯肼。重排通过形成氮丙啶中间体而进行,在某些情况下可以将其分离。合成的1-[((2,4-二硝基苯基)氨基] -1 H中的2-硝基-吡唑-4-羧酸酯可以通过氨基的酰化然后使用H 2 -Pd / C氢化-脱酰在两个步骤中选择性地还原。