作者:Diane Zimmermann、Povl Krogsgaard-Larsen、Jean-Daniel Ehrhardt、Ulf Madsen、Yves L Janin
DOI:10.1016/s0040-4020(98)00579-1
日期:1998.8
2,3-Dihydropyrazolo[3,2-b]oxazoles were used as intermediates in a new method for preparation of N1-methyl-3-hydroxypyrazoles. Synthesis of this bicyclic system was achieved either by alkylation of 3-hydroxypyrazole with 1,2-dibromoethane or, with better yields, by cyclization of 1-tosyl-2-(2-hydroxyethyl)pyrazol-3-ones via a nitrogen to oxygen transfer of the tosyl group. Alkylation with methyl t
2,3-二氢吡唑并[3,2- b ]恶唑被用作制备N1-甲基-3-羟基吡唑的新方法的中间体。该双环体系的合成可以通过将3-羟基吡唑与1,2-二溴乙烷烷基化来实现,也可以通过将1-甲苯磺酰基-2-(2-羟乙基)吡唑-3-酮经氮环合成氧来获得更高的收率。甲苯磺酰基基团的转移。用三氟甲磺酸甲酯烷基化,然后用碘化钠将二氢恶唑开环,得到1-甲基-2-(2-碘乙基)吡唑。通过氰化然后脱氰乙基化反应或通过N 2除去N 2上的碘乙基链以得到目标3-羟基吡唑。消除碘化氢,然后对所得的乙烯基衍生物进行基于碘的氧化。使用后一种方法,可以从相应的2,3-二氢吡唑并[3,2- b ]恶唑制得1-甲基-3-羟基吡唑,产率为58-73%。