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首页> 外文期刊>Chemistry: A European journal >Ethynyl benziodoxolones for the direct alkynylation of heterocycles: Structural requirement, improved procedure for pyrroles, and insights into the mechanism
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Ethynyl benziodoxolones for the direct alkynylation of heterocycles: Structural requirement, improved procedure for pyrroles, and insights into the mechanism

机译：乙炔基苯并恶唑啉用于杂环的直接烷基化：结构要求，吡咯的改进程序以及对该机理的见解

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This report describes a full study of the gold-catalyzed direct alkynylation of indoles, pyrroles, and thiophenes using alkynyl hypervalent iodine reagents, especially the study of the structural requirements of alkynyl benziodoxolones for an efficient acetylene transfer to heterocycles. An improved procedure for the alkynylation of pyrroles using pyridine as additive is also reported. Nineteen alkynyl benziodoxol(on)es were synthesized and evaluated in the direct alkynylation of indoles and/or thiophenes. Bulky silyl groups as acetylene substituents were optimal. Nevertheless, transfer of aromatic acetylenes to thiophene was achieved for the first time. An accelerating effect of a methyl substituent in both the 3-and 6-position of triisopropylsilylethynyl-1,2-benziodoxol-3(1H)-one (TIPS-EBX) on the reaction rate was observed. Competitive experiments between substrates of different nucleophilicity, deuterium labeling experiments, as well as the regioselectivity observed are all in agreement with electrophilic aromatic substitution. Gold(III) 2-pyridinecarboxylate dichloride was also an efficient catalyst for the reaction. Investigations indicated that gold(III) could be eventually reduced to gold(I) during the process. As a result of these investigations, a π activation or an oxidative mechanism are most probable for the alkynylation reaction.
机译：该报告描述了使用炔基高价碘试剂对金催化的吲哚，吡咯和噻吩直接炔基化的全面研究，尤其是炔基苯并恶唑烷酮对乙炔有效转移至杂环的结构要求的研究。还报道了使用吡啶作为添加剂的吡咯烷基炔化的改进方法。合成并在吲哚和/或噻吩的直接炔基化反应中合成了19个炔基苯并恶唑醇。最佳的甲硅烷基取代基是庞大的甲硅烷基。尽管如此，还是第一次实现了芳族乙炔向噻吩的转移。观察到在三异丙基甲硅烷基乙炔基-1，2-苯并恶多酚-3（1H）-1（TIPS-EBX）的3-位和6-位的甲基取代基对反应速率的促进作用。不同亲核性底物之间的竞争性实验，氘标记实验以及观察到的区域选择性均与亲电子芳族取代一致。 2-吡啶甲酸羧二金（III）也是该反应的有效催化剂。研究表明，在此过程中金（III）最终可能还原为金（I）。这些研究的结果是，炔烃化反应最有可能发生π活化或氧化机理。

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