Plessel Kristin N, Jones Amanda C, Wherritt Daniel J, Maksymowicz Rebecca M, Poweleit Eric T, Reich Hans J
Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, United States.
Org Lett. 2015 May 15;17(10):2310-3. doi: 10.1021/acs.orglett.5b00650. Epub 2015 Apr 27.
Unexpectedly high rates of reaction between alkyllithium reagents and amides, compared to esters and ketones, were observed by Rapid Inject NMR and competition experiments. Spectroscopic investigations with 4-fluorophenyllithium (ArLi, mixture of monomer and dimer in THF) and a benzoate ester identified two reactive intermediates, a homodimer of the tetrahedral intermediate, stable below -100 °C, and a mixed dimer with ArLi. Direct formation of dimers suggested that the ArLi dimer may be the reactive aggregate rather than the usually more reactive monomer. In contrast, RINMR experiments with ketones demonstrated that the ArLi monomer was the reactive species.
通过快速注入核磁共振（Rapid Inject NMR）和竞争实验观察到，与酯类和酮类相比，烷基锂试剂与酰胺之间的反应速率意外地高。用4-氟苯基锂（ArLi，在四氢呋喃（THF）中为单体和二聚体的混合物）和苯甲酸酯进行的光谱研究确定了两种反应中间体，一种是四面体中间体的同二聚体，在-100°C以下稳定，另一种是与ArLi的混合二聚体。二聚体的直接形成表明，ArLi二聚体可能是反应性聚集体，而不是通常反应性更强的单体。相比之下，用酮类进行的RINMR实验表明，ArLi单体是反应性物种。
