Transition-metal-catalyzed cross-coupling reactions between naturally abundant sp3-hybridized carbon centers facilitate access to diverse molecules with complex three-dimensional structures. Organometallic compounds are among one of the most powerful reagents that are broadly used in carbon–carbon bondformations. Although sp2-hybridized organometallic compounds are widely employed in cross-couplings, sp3-hybridized
Gold-catalyzed synthesis of 1,3-disubstituted benzenes through tandem allylation/cyclization reaction of alkynals
作者:Sabyasachi Bhunia、Shariar Md. Abu Sohel、Chao-Chin Yang、Shie-Fu Lush、Fwu-Ming Shen、Rai-Shung Liu
DOI:10.1016/j.jorganchem.2008.10.049
日期:2009.2
Treatment of alkynals with 2-substituted allylsilanes and PPh3AuCl/AgOTf (5/3 mol%) catalyst led to formation of 1,3-disubstituted benzenes efficiently. This reaction sequence comprises an initial allylation of aldehyde, followed by cycloisomerization of enynes; PPh3AuOTf is active in both steps.
A variety of aromatichydrocarbons bearing multiple alkyl substituents are accessible with perfect regiocontrol in a one-pot reaction starting from cyclohexenones and their aromatic analogues [Eq. (1)]. The present methodology can be further extended to the synthesis of polycyclic aromatichydrocarbons. The drawbacks encountered in the Friedel-Crafts reaction are resolved since the reaction proceeds
Regioselective Arene Functionalization: Simple Substitution of Carboxylate by Alkyl Groups
作者:Tobias Krüger、Katja Vorndran、Torsten Linker
DOI:10.1002/chem.200901774
日期:2009.11.9
from toluic and naphthoic acids, the carboxylate group was conveniently substituted by alkyl halides by Birch reduction and subsequent decarbonylation. The method is characterized by inexpensive starting materials and reagents, and methylation of arenes was realized. Besides simple alkyl substituents, the scope of arene functionalization was extended by benzyl, fluoro, amino, and ester groups. We were
that the selective formation of a monotransmetalated FeII species during the catalytic regime counterintuitively does not alone ensure an efficient suppression of the nucleophile homocoupling side reaction. It is conversely shown that a fine control of the transmetalation degree of the transient FeIII intermediates obtained after the activation of alkyl electrophiles by a single-electron transfer (SET)
控制有机铁 (II) 物种的金属转移程度是众多 Fe 催化交叉偶联中的关键参数,以确保该过程的成功。然而,在本报告中,我们证明了在催化机制中选择性形成单金属化 Fe II物质并不能单独确保有效抑制亲核试剂均偶联副反应。相反地表明,通过单电子转移(SET)激活烷基亲电试剂后获得的瞬态 Fe III中间体的金属转移程度的精细控制,可使用 σ 供体添加剂实现,解释了交叉的选择性。耦合途径。该报告首次表明 Fe 的两个配位层II静息态和 Fe III短寿命中间体必须在催化过程中进行有效调整,以确保高耦合选择性。