Parrales Gloria M, Hollin Nina C, Song Fubin, Lyu Yangyang, Martin Anne-Marie O, Strom Alexandra E
Department of Chemistry, Smith College, Northampton, Massachusetts 01063, United States.
J Org Chem. 2024 Sep 6;89(17):12462-12466. doi: 10.1021/acs.joc.4c01401. Epub 2024 Aug 16.
We report the mechanism of the iron-catalyzed oxidative α-amination of ketones with sulfonamides. Using linear free energy relationships, competition experiments, and identification of reaction intermediates, we have found that the mechanism of this reaction proceeds through rate-limiting electron transfer to 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) from an iron enolate in the process of forming an α-DDQ adduct. The adduct then serves as the electrophile for substitution with sulfonamide nucleophiles, accelerated by iron and additional DDQ. This mechanistic study rules out formation of an α-carbocation intermediate and purely radical mechanistic hypotheses.
我们报道了铁催化酮与磺酰胺进行氧化α-胺化反应的机理。通过线性自由能关系、竞争实验以及反应中间体的鉴定，我们发现该反应的机理是在形成α-2,3-二氯-5,6-二氰基-1,4-苯醌（DDQ）加合物的过程中，从烯醇铁向DDQ进行限速电子转移。然后该加合物作为亲电试剂与磺酰胺亲核试剂发生取代反应，铁和额外的DDQ可加速此反应。这项机理研究排除了α-碳正离子中间体的形成以及纯自由基机理的假设。
