Catalyst-Free Regioselective C-3 Nitrosation of Imidazopyridines with tert-Butyl Nitrite under Neutral Conditions
摘要:
We have successfully developed a novel and efficient catalyst-free method for the synthesis of 3-nitroso-substituted imidazopyridines, from readily available imidazo[1,2-a]pyridines and tert-butyl nitrite, in good to excellent yields. Importantly, the use of transition-metal catalysts, stoichiometric amounts of acids, and toxic or potentially dangerous oxidants is avoided. This easy and practical method complements nitrosation reactions by expanding the scope and practicality, and should attract much attention in synthetic and pharmaceutical chemistry.
Regioselective, Solvent- and Metal-Free Chalcogenation of Imidazo[1,2-<i>a</i>
]pyridines by Employing I<sub>2</sub>
/DMSO as the Catalytic Oxidation System
作者:Jamal Rafique、Sumbal Saba、Alisson R. Rosário、Antonio L. Braga
DOI:10.1002/chem.201600800
日期:2016.8.8
molecular‐iodine‐catalyzed chalcogenations (S and Se) of imidazo[1,2‐a]pyridines were achieved by using diorganoyl dichalcogenides undersolvent‐freeconditions. This approach afforded the desired products that had been chalcogenated regioselectively at the C3 position in up to 96 % yield by using DMSO as an oxidant, in the absence of a metal catalyst, and under an inert atmosphere. This mild, green approach allowed
通过在无溶剂条件下使用二有机基二卤化氢实现咪唑并[1,2- a ]吡啶的高效分子碘催化硫属元素化(S和Se)。通过使用DMSO作为氧化剂,在没有金属催化剂的情况下,并且在惰性气氛下,该方法提供了所需的产物,该产物已经在C3位置进行了区域硫磺化,产率高达96%。这种温和的绿色方法可以制备具有结构多样性的不同类型的硫族化咪唑并[1,2- a ]吡啶。此外,当前协议还扩展到其他N杂环核。
KIO
<sub>4</sub>
‐mediated Selective Hydroxymethylation/Methylenation of Imidazo‐Heteroarenes: A Greener Approach
hydroxymethylation or methylenation of imidazo-heteroarenes with formaldehyde, generated in situ via the oxidative cleavage of ethylene glycol or glycerol (renewable reagents) through the Malaprade reaction. In the presence of ethylene glycol, a series of 3-hydroxymethyl-imidazo-heteroarenes was obtained in good to excellent yields. These compounds are important intermediates to access pharmaceutical drugs
在此,我们报告了一种 KIO 4介导的、可持续的和化学选择性的方法,用于一锅 C(sp 2 )-H 键羟甲基化或咪唑杂芳烃与甲醛的甲基化,通过乙二醇或甘油的氧化裂解原位生成。可再生试剂)通过马拉普拉德反应。在乙二醇的存在下,以良好到极好的收率获得了一系列 3-羟甲基-咪唑并杂芳烃。这些化合物是获取药物(例如唑吡坦)的重要中间体。此外,通过使用甘油,双(咪唑并[1,2 - a ]吡啶-3-基)甲烷衍生物以良好到优异的产率被选择性地获得。
Direct, Metal-free C(sp<sup>2</sup>
)−H Chalcogenation of Indoles and Imidazopyridines with Dichalcogenides Catalysed by KIO<sub>3</sub>
作者:Jamal Rafique、Sumbal Saba、Marcelo S. Franco、Luana Bettanin、Alex R. Schneider、Lais T. Silva、Antonio L. Braga
DOI:10.1002/chem.201705404
日期:2018.3.15
synthesis of 3‐Se/S‐indoles and imidazo[1,2‐a]pyridines through direct C(sp2)−H bond chalcogenation of heteroarenes with half molar equivalents of different dichalcogenides, using KIO3 as a non‐toxic, easy‐to‐handle catalyst and a stoichiometric amount of glycerol. The reaction features are high yields, based on atom economy, easy performance on gram‐scale, metal‐ and solvent‐free conditions as well as applicability
本文中,我们报告了一种更环保的协议,该方法通过杂芳烃的直接C(sp 2)-H键硫代半数当量的不同二硫代半乳糖苷合成3-Se / S-吲哚和咪唑并[1,2- a ]吡啶KIO 3是一种无毒,易于操作的催化剂和化学计量的甘油。该反应的特征是基于原子经济性的高收率,在克级,无金属和无溶剂条件下易于操作以及适用于不同类型的N-杂芳烃。
Solvent and catalyst‐free synthesis of imidazo[1,2‐a]pyridines by grindstone chemistry
作者:Kumar Godugu、Chinna Gangi Reddy Nallagondu
DOI:10.1002/jhet.4164
日期:2021.1
The present work describes the solvent and catalyst‐free synthesis of imidazo[1,2‐a]pyridines in excellent to nearly quantitative yields from 2‐aminopyridines and a wide variety of ω‐bromomethylketones using a grindstone procedure at 25°C to 30°C for 3 to 5 minutes. The absolute structure of the compound, 2‐(3‐bromophenyl)‐7‐methylimidazo[1,2‐a]pyridine is determined by X‐ray crystallography. This
We describe herein a catalyst-free selective C−H sulfenylation of imidazo[1,2-a]pyridines using sulfonothioates as odorless source of thioarylated reagent in an aqueous medium. The method works for a variety of substitutedimidazo[1,2-a]pyridines with broad functional group tolerance. The methodology has been extends to selective sulfernylation of indoles and imidazothiazoles. The sulfonothioates are