An Efficient Synthesis of Substituted Pyrazoles from One-Pot Reaction of Ketones, Aldehydes, and Hydrazine Monohydrochloride
作者:Vit Lellek、Cheng-yi Chen、Wanggui Yang、Jie Liu、Xuebao Ji、Roger Faessler
DOI:10.1055/s-0036-1591941
日期:2018.5
hydrazine monohydrochloride readily formed pyrazoline intermediates under mild conditions. Oxidation of pyrazolines, in situ, employing bromine afforded a wide variety of pyrazoles. The methodology offers a fast, and often chromatography-free protocol for the synthesis of 3,4,5-substituted pyrazoles in good to excellent yields. Alternatively, a more benign oxidation protocol affords 3,5-disubstituted or
开发了一种高效、单锅且无金属的制备多克规模的 3,5-二取代和 3,4,5-三取代吡唑的方法。在温和条件下,酮、醛和肼单盐酸盐的一锅缩合容易形成吡唑啉中间体。使用溴原位氧化吡唑啉得到多种吡唑。该方法为合成 3,4,5-取代吡唑的 3,4,5-取代吡唑类化合物提供了一种快速且通常无需色谱的方案,收率非常好。或者,通过简单地在 DMSO 中在氧气下加热吡唑啉,更温和的氧化方案提供 3,5-二取代或 3,4,5-三取代的吡唑。