Metal-free remote-site C–H alkenylation: regio- and diastereoselective synthesis of solvatochromic dyes,Green Chemistry

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Metal-free remote-site C–H alkenylation: regio- and diastereoselective synthesis of solvatochromic dyes
Green Chemistry ( IF 9.3 ) Pub Date : 2017-12-27 00:00:00 , DOI: 10.1039/c7gc03436a
María José Albaladejo _{1,

2,

3,

4,

5} , María José González-Soria _{1,

2,

3,

4,

5} , Francisco Alonso _{1,

2,

3,

4,

5}

Affiliation

Lately, transition-metal catalysed C–H alkenylation of nitrogen heterocycles has gained increasing attention, often with the intervention of complex and expensive catalytic systems. On the other hand, both, chalcones and indolizines are versatile families of compounds with applications in diverse research areas, including materials science, because of their prominent photophysical attributes. We set forth herein the metal-free regio- and diastereoselective C–H alkenylation of indolizines through a very simple and mild acid–base approach. The most fascinating fact in this remote-site C_sp²–C_sp² bond formation is that only one starting material is utilised, which undergoes a formal self-alkenylation to integrate a chalcone moiety and furnish a new family of dyes; a plausible reaction mechanism has been put forward. A one-pot multicomponent protocol was conceived that generates the starting indolizine in situ and has been extended to a multi-gram scale synthesis with equal efficiency. The dyes show a single structure in the solid state but two stable structures in solution (rotamers). Preliminary studies on the optical properties of the dyes reveal a particle-size dependent colour in the solid state and solvatochromism (i.e., different colours in solution depending on the solvent polarity). Remarkably, the solvatochromic behaviour was also displayed in plastics. We believe that this finding opens new avenues in the fields of heterocyclic chemistry, dyes, and materials science.

中文翻译：

无金属的远程C–H链烯基化：溶剂变色染料的区域和非对映选择性合成

最近，过渡金属催化的氮杂环的CH链烯基化受到越来越多的关注，通常是在复杂而昂贵的催化体系的干预下进行的。另一方面，由于查耳酮和吲哚嗪具有显着的光物理特性，它们都是通用的化合物家族，在包括材料科学在内的各种研究领域中都有应用。我们在这里提出了一种非常简单且温和的酸碱法对吲哚嗪进行无金属的区域和非对映选择性的CH链烯基化。在此远程站点C _{sp ²} –C _sp_^2中，最令人着迷的事实键的形成是仅使用一种原料，该原料经过正式的自烯基化作用以整合查耳酮部分并提供新的染料家族。提出了合理的反应机制。设想了一种一锅多组分方案，该方案原位生成起始吲哚利嗪，并已被扩展至具有相等效率的多克级合成。染料在固态时显示单个结构，但在溶液中（旋转剂）显示两个稳定结构。对染料光学性质的初步研究表明，在固态和溶剂致变色作用下，颗粒大小取决于颜色（即，溶液中的颜色取决于溶剂的极性）。显着地，在塑料中也表现出溶剂变色行为。我们相信，这一发现为杂环化学，染料和材料科学领域开辟了新途径。

更新日期：2018-02-06

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