Visible-Light-Mediated Oxidative Dimerization of Arylalkynes in the Open Air: Stereoselective Synthesis of (<i>Z</i>)-1,4-Enediones
作者:Donglei Wei、Fushun Liang
DOI:10.1021/acs.orglett.6b02926
日期:2016.11.18
An organic photoredox catalytic one-pot protocol is developed for the highly stereoselective synthesis of (Z)-1,4-enediones. The reaction starts directly from alkyne precursors, using 4-(4-cyanophenyl)-2,6-diphenylpyrylium tetrafluoroborate (CN-TPT) as an efficient photosensitizer and dioxygen in the air as a green oxidant. A Csp–Csp oxidative coupling/[4 + 2] cyclization (with dioxygen)/fragmentive
desirable, especially since 1 : 6-addition is comparatively uncommon3. We have done this by reducing several substituted dibenzoylethylenes with aluminium isopropoxide in isopropyl alcohol, a reagent known to attack carbonyl groups while leaving olefinic linkages intact. The reductionproducts were invariably the corresponding diphenacyls, identified (after chromatographic adsorption) by mixed melting points
Rotational isomerism in 1,4-diarylbut-2-ene-1,4-dione radical anions: an electron paramagnetic resonance study
作者:M. Luisa T. M. B. Franco、M. Celina R. L. R. Lazana、Bernardo J. Herold
DOI:10.1039/ft9928801977
日期:——
The radicalanions of (Z)- and (E)-1,4-diarylbut-2-ene-1,4-diones 1–8 have been obtained by electrolytic reduction in dimethylformamide. Identical EPR spectra are recorded at room temperature for both the (Z)- and (E)-isomers evidencing rapid (Z)–(E) interconversion. Individual conformers are not observed for radicalanions derived from either diphenyl, bis(p-tolyl) or bis(p-anisyl) derivatives 1˙––6˙–
is disclosed. The newly developed reaction provides practical access to 1,2-diketones and (Z)-1,4-enediones in moderate to good yields with absolute regio- and stereoselectivity. Mechanistic studies of the reaction suggest that tetraketone intermediates might undergo a photocatalytic energy transfer from the excited photocatalyst to form biradical-like (n,π*) states of ketones.
公开了使用有机染料作为光催化剂在可见光照射下1,3-二酮的有氧氧化裂解。新开发的反应以中等至良好的产率和绝对的区域选择性和立体选择性提供了实际获得 1,2-二酮和 ( Z )-1,4-烯二酮的方法。该反应的机理研究表明,四酮中间体可能会经历激发光催化剂的光催化能量转移,形成酮的双自由基 (n,π*) 态。