在这里,我们将苯并[ b ]吩噻嗪的阴离子描述为可见光激发下的超级还原剂物种。与 N-取代的吩噻嗪或苯并吩噻嗪相反,该分子具有极高的还原能力,可在 -3.51 V vs SCE 的电位下促进基于单电子转移的还原裂解。作为证据,大量的芳基氯底物已被还原裂解以制造异吲哚酮和羟吲哚类分子。此外,芳基-氯键已均裂,生成芳基自由基,可用于 C-C 交叉偶联或 C-P 键形成反应。为了证明其极端的还原能力,一些芳基氟化物键被裂解以产生芳基自由基。包括稳态和时间分辨光谱技术在内的详细光物理研究解释了分子在光激发下的行为,以及与其反应模式相关的行为。理论计算表明,苯并吩噻嗪阴离子在基态时会稍微起皱,因为该分子本质上是反芳香族的。相反,激发态几何形状是平面的,这也接近一次电子转移后的中间体的几何形状。阴离子物质的反芳香性的减弱是其高度还原行为的部分原因。
Nickel or Phenanthroline Mediated Intramolecular Arylation of sp<sup>3</sup> C–H Bonds Using Aryl Halides
作者:William C. Wertjes、Lydia C. Wolfe、Peter J. Waller、Dipannita Kalyani
DOI:10.1021/ol402869h
日期:2013.12.6
the intramolecular arylation of sp3 C–Hbonds adjacent to nitrogen using aryl halides is described. Arylation was accomplished using either Ni(COD)2 or 1,10-phenanthroline in substoichiometric amounts, and the reaction conditions were applied to a variety of electronically differentiated benzamide substrates. Preliminary studies suggest a mechanism involving aryl and alkyl radical intermediates.
mild visible‐light‐induced Pd‐catalyzed intramolecular C−H arylation of amides is reported. The method operates by cleavage of a C(sp2)−O bond, leading to hybrid aryl Pd‐radical intermediates. The following 1,5‐hydrogen atom translocation, intramolecular cyclization, and rearomatization steps lead to valuable oxindole and isoindoline‐1‐one motifs. Notably, this method provides access to products with
nitrenium (NHN) salts, the analogues of N-heterocyclic carbenes, have attracted considerable interest. However, relatively little is known about their catalytic ability beyond their Lewis acid catalysis. Herein, we describe that NHNs can serve as catalytic electron acceptors for charge transfer complex photoactivations. We showcase that, under blue light irradiation, the NHN salts could catalyze the
halogen bonding (XB) for the generation of aryl radicals from aryl halides under blue light irradiation and applied it in radical generation/1,5-hydrogen-atom transfer/radical cyclization cascade reactions for the synthesis of oxindoles and isoindolinones. On the basis of experimental studies, we propose that DBU can serve as a suitable XB acceptor with aryl halides for the formation of a photoactive
radical-mediated intramolecular coupling of two C–H bonds of N,N-diisopropyl benzamides was developed. The reactions can proceed in moderate to high yield and with excellent chemoselectivity. A reaction sequence of the formation of an alkyl radical via oxidative cleavage of alkyl C–H bond and the formation of lactam ring via intramolecular homolytic aromatic substitution was proposed.