symmetrical trans-stilbene oxide, the syn- versus anti-bromohydrins ratio ranged between 88/12 and 30/70, by varying the reaction temperature from 20 to −30 °C. In the case of nonsymmetrical para-substituted trans-2,3-diaryloxiranes, the regioselectivity is determined by electroniceffects. If one phenyl bears a strong electron-withdrawing group (as NO2 or CF3), the nucleophilic attack is totally on the
A high yielding synthesis of stilbene oxides using ammonium ylides has been developed. It turned out that the amine leaving group plays a crucial role as trimethylamine gives higher yields than DABCO or quinuclidine. The amine group also influences the diastereoselectivity, and detailed DFT calculations to understand the key parameters of these reactions have been carried out.
Photocatalyzed Transition‐Metal‐Free Oxidative Cross‐Coupling Reactions of Tetraorganoborates**
作者:Arif Music、Andreas N. Baumann、Florian Boser、Nicolas Müller、Florian Matz、Thomas C. Jagau、Dorian Didier
DOI:10.1002/chem.202005282
日期:2021.3
salts undergo selective coupling reactions under blue light irradiation in the presence of catalytic amounts of transition‐metal‐free acridinium photocatalysts to furnish unsymmetrical biaryls, heterobiaryls and arylated olefins. This represents an interesting conceptual approach to forge C−C bonds between aryl, heteroaryl and alkenyl groups under smooth photochemical conditions. Computational studies
Enantioselective Synthesis of (Thiolan-2-yl)diphenylmethanol and Its Application in Asymmetric, Catalytic Sulfur Ylide-Mediated Epoxidation
作者:Hsin-Yi Wu、Chih-Wei Chang、Rong-Jie Chein
DOI:10.1021/jo400648f
日期:2013.6.7
This work describes an expeditious and efficient preparation of enantiopure (thiolan-2-yl)diphenylmethanol (2) featuring a double nucleophilic substitution and Shi epoxidation as key steps. One of the applications of its benzyl ether derivative to asymmetric sulfur ylide-mediated epoxidation with up to 92% ee (14 examples) was also demonstrated herein.
Epoxide Formation by Indirect Electroreductive Coupling between Aldehydes or Ketones and Activated<i>gem</i>-Dichloro Compounds
作者:J. P. Paugam、S. Oudeyer、E. Léonel、J.-Y. Nédélec
DOI:10.1055/s-2004-815915
日期:——
Epoxides are prepared by indirect electroreductive coupling of carbonyl compounds (aldehydes or ketones) and activated gem-dichloro compounds. This process is more efficient with aryl ketones than with aryl aldehydes. Though yields are only moderate, this method offers the valuable advantage of avoiding the use of strong bases or peroxides.