Williams Anietie W, Gilmore Kerry M
Department of Chemistry, University of Connecticut, 55 N Eagleville Rd, Storrs, CT, 06269.
Chemistry. 2024 Dec 13;30(70):e202403410. doi: 10.1002/chem.202403410. Epub 2024 Nov 7.
Cross-coupling reactions for constructing C-N bonds represent a pivotal advancement in chemical science. Traditional methodologies, including nucleophilic aromatic substitution (SNAr) and transition metal-catalyzed cross-couplings, have limitations concerning aryl scope, reliance on toxic and costly transition-metal catalysts, and issues related to atom economy and waste generation from ligands and additives. In this work, we introduce a novel method for aminating neutral, electron-rich, and electron-deficient aryl halides, eliminating the need for transition metals. Our approach involves the activation of aryl halides using solvated electrons generated from granulated lithium and sonication. This serves as a sustainable source of reducing power, facilitating the efficient formation of C-N bonds under near ambient conditions. Competitive selectivity studies between halide and ester functionalities were explored. Reaction scope and conducted mechanistic studies which supported the proposed radical-nucleophilic substitution (SRN) mechanism for the reaction. Notably, the developed reaction has a highly competitive reductive dehalogenation pathway during the C-N coupling reaction, and this mechanistic divergency was thoroughly explored. This work not only broadens the scope of C-N coupling reactions which typically employs aryl bromides and iodides and rarely aryl fluorides which is also equally abundant, but also introduces a new way to do C-N coupling reactions using solvated electrons.
构建C-N键的交叉偶联反应是化学科学中的一项关键进展。传统方法,包括亲核芳香取代(SNAr)和过渡金属催化的交叉偶联,在芳基范围、对有毒且昂贵的过渡金属催化剂的依赖以及与原子经济性和配体及添加剂产生的废物相关的问题上存在局限性。在这项工作中,我们介绍了一种用于对中性、富电子和缺电子芳基卤化物进行胺化的新方法,无需过渡金属。我们的方法涉及使用由粒状锂和超声处理产生的溶剂化电子来活化芳基卤化物。这作为一种可持续的还原力来源,有助于在接近环境条件下高效形成C-N键。探索了卤化物和酯官能团之间的竞争选择性研究。研究了反应范围并进行了机理研究,这些研究支持了所提出的该反应的自由基亲核取代(SRN)机理。值得注意的是,所开发的反应在C-N偶联反应过程中有一条极具竞争力的还原脱卤途径,并且对这种机理分歧进行了深入探索。这项工作不仅拓宽了通常使用芳基溴化物和碘化物且很少使用同样丰富的芳基氟化物的C-N偶联反应的范围,还引入了一种使用溶剂化电子进行C-N偶联反应的新方法。