Wasfy Nour, Rasheed Faizan, Robidas Raphaël, Hunter Isabelle, Shi Jiaqi, Doan Brian, Legault Claude Y, Fishlock Dan, Orellana Arturo
Department of Chemistry, York University 4700 Keele Street Toronto ON Canada M3J 1P3
Department of Chemistry, Centre in Green Chemistry and Catalysis, University of Sherbrooke 2500 Boulevard de l'Université Sherbrooke Québec J1K 2R1 Canada
Chem Sci. 2020 Dec 10;12(4):1503-1512. doi: 10.1039/d0sc03304a.
We report a mild palladium-catalyzed method for the selective allylation of 4-alkylpyridines in which highly basic pyridylic anions behave as soft nucleophiles. This method exploits alkylidene dihydropyridines, which are semi-stable intermediates readily formed using a 'soft-enolization' approach, in a new mechanistic manifold for decarboxylative allylation. Notably, the catalytic generation of pyridylic anions results in a substantially broader functional group tolerance compared to other pyridine allylation methods. Experimental and theoretical mechanistic studies strongly suggest that pyridylic anions are indeed the active nucleophiles in these reactions, and that they participate in an outer-sphere reductive elimination step. This finding establishes a new p boundary of 35 for soft nucleophiles in transition metal-catalyzed allylations.
我们报道了一种温和的钯催化方法，用于4-烷基吡啶的选择性烯丙基化反应，其中高碱性吡啶阴离子表现为软亲核试剂。该方法利用亚烷基二氢吡啶，它们是通过“软烯醇化”方法容易形成的半稳定中间体，用于脱羧烯丙基化的新机理体系。值得注意的是，与其他吡啶烯丙基化方法相比，吡啶阴离子的催化生成导致了实质上更广泛的官能团耐受性。实验和理论机理研究强烈表明，吡啶阴离子确实是这些反应中的活性亲核试剂，并且它们参与外层还原消除步骤。这一发现确立了过渡金属催化烯丙基化反应中软亲核试剂的新p边界为35。
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