从N-桥联稠合双环化合物(如咪唑并[1,2- a ]吡啶,咪唑并[1,2- a ]嘧啶和咪唑并[2,1- b ]噻唑)合成的简便且环境友好的方案已经开发了可商购的原料。反应是通过NBS介导的原位形成相应芳族酮,1,3-二酮,β-酮酯的α-溴化中间体进行的,然后用适当的亲核试剂进行捕集,以提供在金属-金属化条件下高收率的这些通用的咪唑稠合双环杂环化合物。免费条件。
tetrabromide mediated oxidative carbon–nitrogen bond formation of 2-aminopyridines or 2-aminopyrimidines with β-keto esters or 1,3-diones, leading to a variety of complex imidazo[1,2-α]pyridines or imidazo[1,2-α]pyrimidines, is reported. The reactions were realized under mild and metal-free conditions.
2-Aminopyridines as an α-Bromination Shuttle in a Transition Metal-Free One-Pot Synthesis of Imidazo[1,2-<i>a</i>
]pyridines
作者:Irwan Iskandar Roslan、Kian-Hong Ng、Gaik-Khuan Chuah、Stephan Jaenicke
DOI:10.1002/adsc.201501012
日期:2016.2.4
A wide range of imidazo[1,2‐a]pyridines are accessible from cheap and readily available 2‐aminopyridines and 1,3‐dicarbonyl compounds using a unique CBrCl3/2‐aminopyridine system for bromination at the α‐carbon. 2‐Aminopyridine is not only the substrate but also acts as a bromination shuttle, transferring the bromine atom from CBrCl3 to the α‐carbon of the 1,3‐dicarbonyl. The reaction mechanism involves
使用独特的CBrCl 3 / 2-氨基吡啶体系在α-碳上进行溴化,可以从便宜且容易获得的2-氨基吡啶和1,3-二羰基化合物中获得各种咪唑并[1,2- a ]吡啶。2-氨基吡啶不仅是底物,而且还用作溴化穿梭,将溴原子从CBrCl 3转移到1,3-二羰基的α-碳上。该反应机理涉及一系列可逆步骤,包括具有环状过渡态的加成反应,以形成溴血红素中间体。在这种无过渡金属的单锅合成中,在温和的条件下和较短的反应时间下,分离出的产率高达97%。
Synthesis of Imidazo[1,2-a]pyridines by the Bis(acetyloxy)(phenyl)-λ³-iodane-Mediated Oxidative Coupling of 2-Aminopyridines with β-Keto Esters and 1,3-Diones
作者:Wei Yu、Xianpei Wang、Lijuan Ma
DOI:10.1055/s-0030-1260106
日期:2011.8
2-aminopyridines and β-keto esters by using bis(acetyloxy)(phenyl)-λ³-iodane as an oxidant and borontrifluoride etherate as a catalyst. The amount of catalyst plays a key role in determining the course of the reaction. Whereas the use of 0.2 equivalents of catalyst ensures the generation of imidazo[1,2-a]pyridines, raising the amount of catalyst to 1.0 equivalents results in exclusive α-acetoxylation of
咪唑并[1,2一]吡啶-3-羧酸盐,可直接由2-氨基吡啶和β酮酯通过使用双(乙酰基氧基)制备(苯基)-λ ³ -iodane作为氧化剂和三氟化硼醚作为催化剂。催化剂的量在确定反应过程中起关键作用。尽管使用0.2当量的催化剂可确保生成咪唑并[1,2- a ]吡啶,但将催化剂的量提高至1.0当量可导致β-酮酯的独家α-乙酰氧基化。2-氨基吡啶也可以与1,3-二酮反应,得到3-酰基咪唑并[1,2- a ]吡啶。 杂环-多环-环化-氧化-偶联
TBAI-catalyzed oxidative coupling of aminopyridines with β-keto esters and 1,3-diones—synthesis of imidazo[1,2-a]pyridines
作者:Lijuan Ma、Xianpei Wang、Wei Yu、Bing Han
DOI:10.1039/c1cc13568f
日期:——
TBAI could catalyze the direct oxidative CâN coupling of 2-aminopyridines with β-keto esters and 1,3-diones, which affords imidazo[1,2-a]pyridines as the products. The reaction was realized under metal-free conditions by using tert-butyl hydroperoxide (TBHP) as the oxidant.
Photocatalytic regeneration of brominating agent in the visible light-mediated synthesis of imidazo[1,2-<i>a</i>]pyridines
作者:Irwan Iskandar Roslan、Kian-Hong Ng、Stephan Jaenicke、Gaik-Khuan Chuah
DOI:10.1039/c9cy00141g
日期:——
supporting evidence of a reductive quenching pathway. The avoidance of stoichiometric excess of the halogen or peroxide oxidants for halide regeneration makes this protocol an environmentally-friendly synthesis with low E-factor.
在可见光介导的光催化下,将1,3-二羰基与2-氨基吡啶偶联可以得到各种各样的咪唑并[1,2- a ]吡啶。使用便宜的和可商购的荧光素染料赤藓红B作为光氧化还原催化剂,KBr作为卤化剂进行原位溴化。该方案的特征在于使用催化量的卤化剂,该卤化剂由光催化剂在可见光照射下再生。循环伏安法研究提供了还原性淬灭途径的支持证据。避免化学计量过量的卤素或过氧化物氧化剂用于卤化物的再生,使该方案成为具有低E因子的环境友好的合成方法。