Dess–Martin Periodinane–Mediated Oxidative Aromatization of 1,3,5-Trisubstituted Pyrazolines
作者:Sumit V. Gamapwar、Nilesh P. Tale、Nandkishor N. Karade
DOI:10.1080/00397911.2011.563449
日期:2012.9
Abstract A general method for the oxidative aromatization of 1,3,5-trisubstitutedpyrazolines under mild conditions has been developed using Dess–Martin periodinane as oxidant. GRAPHICAL ABSTRACT
Non-oxidative photoreaction of 1,3,5-triaryl-2-pyrazoline-4-ol (4-methoxy) derivatives
作者:Fatemeh Ebrahimi、Hamid Reza Memarian、Hadi Amiri Rudbari、Olivier Blacque
DOI:10.1016/j.jphotochem.2022.114306
日期:2023.2
light. The results explain the occurrence of a non-oxidative photoreaction, by the expulsion of 4-substitution and elimination of a molecule of water or methanol under the formation of the aromatized pyrazole ring. Density functional theory (DFT) calculations were carried out to support the proposed electron-transfer induced photoreaction mechanism. Natural bond orbital (NBO) analysis explains the preferred
合成了一系列 4-羟基或 4-甲氧基取代的 1,3,5-三芳基-2-吡唑啉,它们的结构,特别是2-吡唑啉环的 4-和 5-氢的反式取向的特点是IR、1 H NMR、13分析C NMR光谱以及单晶结构研究。为了阐明 4-羟基或 4-甲氧基取代对这些化合物的光化学行为的影响,将它们暴露在紫外线下。结果解释了非氧化性光反应的发生,即在芳构化吡唑环的形成下,4-取代基的排出和水或甲醇分子的消除。进行密度泛函理论 (DFT) 计算以支持所提出的电子转移诱导光反应机制。自然键轨道 (NBO) 分析解释了从 N 1中优选的电子脱离过程-原子而不是羟基或甲氧基的氧原子。质子从所涉及的自由基阳离子物质脱离导致形成以杂环的C 5位为中心的自由基中间体。羟基或甲氧基的消除在形成C 4 -未取代的吡唑分子的情况下完成了光反应。
Regioselective Synthesis of 1,3,5-Tri- and 1,3,4,5-Tetrasubstituted Pyrazoles from <i>N</i>-Arylhydrazones and Nitroolefins
作者:Xiaohu Deng、Neelakandha S. Mani
DOI:10.1021/jo7026195
日期:2008.3.1
[GRAPHICS]Two general protocols are developed for the regioselective synthesis of 1,3,5-tri- and 1,3,4,5-tetrasubstituted pyrazoles by the reaction of electron-deficient N-arylhydrazones with nitroolefins. Studies on the stereochemistry of the key pyrazolidine intermediate suggest a stepwise cycloaddition mechanism.
3,4-Dihydro-2H-pyran promoted aerobic oxidative aromatization of 1,3,5-trisubstituted pyrazolines and Hantzsch 1,4-dihydropyridines
An unprecedented facile oxidation of 1,3,5-trisubstitutedpyrazolines and Hantzsch 1,4-dihydropyridines (DHPs) to the corresponding pyrazoles and pyridines was observed, mediated by 3,4-dihydro-2H-pyran in air. The reaction showed excellent reactivity, functional group tolerance, and high yield without using any metal and/or halogen based oxidizing agents.