一些自由基足够稳定以被分离,但大多数要么是不稳定的瞬态物质,要么作为与二聚体形式平衡的亚稳定物质存在,通常是自旋配对 sigma 二聚体或 pi 二聚体(pimer)。为了深入了解二聚化的不同模式,我们合成并评估了一个包含 15 个芳基二氰基甲基自由基的库,以探索导致 sigma 与 pi 二聚化的结构和分子参数。我们通过变温 EPR 光谱测量每个自由基结合的强度,通过紫外-可见光谱和 X 射线晶体学确定二聚体(σ 或 pi 二聚体)的模式,并进行计算分析来评估发散二聚化行为。我们评估了三种不同的假设来解释二聚化行为的差异:(1) 二聚化行为是由自由基自旋密度决定的;(2) 它是由自由基极化率决定的;(3) 它是由二聚体的伦敦分散稳定性决定的。然而,没有单一参数模型本身是可预测的。结合计算的自旋离域度或自由基极化率以及计算的 pi 二聚体中有吸引力的伦敦色散力的估计值的双参数模型导致了对 sigma
Direct Oxidation of Aryl Malononitriles Enabling a Copper-Catalyzed Intermolecular Alkene Carbochlorination
作者:Prakash Basnet、Gang Hong、Charles E. Hendrick、Marisa C. Kozlowski
DOI:10.1021/acs.orglett.0c03941
日期:2021.1.15
A copper-catalyzed carbochlorination of alkenes with aryl malononitriles and chloride is disclosed. This net oxidative transformation proceeds with activated and unactivated alkenes with moderate to excellent yields. Mechanism experiments suggest addition of the malononitrile radical to form a secondary carbon radical which is intercepted by a chloride source. The resultant products can be transformed
Copper Catalyzed Oxidative Arylation of Tertiary Carbon Centers
作者:Prakash Basnet、Melissa B. Sebold、Charles E. Hendrick、Marisa C. Kozlowski
DOI:10.1021/acs.orglett.0c03581
日期:2020.12.18
describe herein a Cu(OTf)2catalyzedoxidative arylation of a tertiary carbon-containing substrate including aryl malononitriles, 3-aryl benzofuran-2-ones, and 3-aryl oxindoles. In some cases, the nitrile groups of the aryl malononitriles undergo further reactions leading to lactones or imines. These reaction conditions are applicable for a range of arenes, including phenols, anilines, anisoles, and heteroarenes
The benzene ring as a dipolarophile: Reactions of monosubstituted benzenes with tetracyanoethylene oxide
作者:A. de la Hoz、C. Pardo、J. Elguero、M. L. Jimeno
DOI:10.1007/bf01045302
日期:1992.1
The reaction of tetracyanoethylene oxide on one hand and toluene, chlorobenzene, fluorobenzene, anisole, and nitrobenzene, on the other, has been studied. Toluene and the halogenobenzenes yield mixture of monoadducts, anisole yield p-methoxyphenylmalononitrile and its dimer and nitrobenzene does not react. These results are discussed with the help of a qualitative orbital model. H-1-NMR analysis of some monoadducts has been carried out.