Efficient conversion of 9-Isopropenylphenanthrene to 4,6,6-trimethyl-6H-benz[de]anthracene in FSO3H; 5,6-dihydro-4H-benzanthracen-4-ium ion and its charge delocalization mode
Preparation of Quaternary Centers via Nickel-Catalyzed Suzuki–Miyaura Cross-Coupling of Tertiary Sulfones
作者:Zachary T. Ariki、Yuuki Maekawa、Masakazu Nambo、Cathleen M. Crudden
DOI:10.1021/jacs.7b10855
日期:2018.1.10
benzylic and allylic sulfones with arylboroxines. A variety of tertiary sulfones, which can easily be prepared via a deprotonation-alkylation route, were reacted to afford symmetric and unsymmetric quaternary products in good yields. We highlight the use of either BrettPhos or Doyle's phosphines as effective ligands for these challenging desulfonative coupling reactions. The utility of this methodology
我们描述了叔苄基和烯丙基砜与芳基环硼烷的镍催化 Suzuki-Miyaura 交叉偶联的开发。可以通过去质子化-烷基化路线轻松制备的各种叔砜反应以良好的收率提供对称和不对称季产物。我们强调使用 BrettPhos 或 Doyle 膦作为这些具有挑战性的脱磺化偶联反应的有效配体。这种方法的实用性在维生素 D 受体调节剂类似物的简明合成中得到了证明。
Palladium-Catalyzed Arylation of α,α-Disubstituted Arylmethanols via Cleavage of a C−C or a C−H Bond To Give Biaryls
The palladium-catalyzedarylation of alpha,alpha-disubstituted arylmethanols with aryl halides proceeds not only via C-H bondcleavage at the ortho-position, but also via cleavage of the sp(2)-sp(3) C-C bond with the liberation of ketones (beta-carbon elimination) to give the corresponding biaryls. Both reactions appear to occur through common arylpalladium(II) alcoholate intermediates. The results
Charge delocalization from cationic substituents into phenanthrene: variation in response among regioisomeric carbocations and carboxonium ions
作者:Kenneth K. Laali、Sandro Hollenstein
DOI:10.1039/a707423i
日期:——
In an effort to assess charge delocalization and stabilities, a series of regioisomeric PAH–C+R2 carbocations (PAH = phenanthrene; R = Me, Ph) were generated from their alcohols by ionization with FSO3H/SO2ClF. Model carboxonium ions were also generated by O-protonation of the isomeric acetyl- and benzoyl-phenanthrenes with FSO3H/SO2ClF. The delocalization paths and the arenium ion character in the resulting carbocations and carboxonium ions are evaluated via low temperature NMR studies; conformational aspects in the carboxonium ions are also addressed. The resulting cations may serve as models for epoxide ring opening in biologically active dihydro diols of several classes of PAHs for which the diol epoxide activation path is believed to be significant in cancer induction.