An efficient and benign method for the regio- and stereoselective synthesis of halohydrins and β-halo ethers from dihydropyrans, dihydrofurans and anhydro sugars in the presence of a halide salt and hydrogen peroxide is presented with tungstate-exchanged takovite as oxidation catalyst.
Photo-induced Alkoxybromination of Olefins by<i>N</i>,<i>N</i>′-Dibromo-2,5-piperazinedione
作者:Akira Sera、Hiroshi Yamada、Kuniaki Itoh
DOI:10.1246/bcsj.53.219
日期:1980.1
Irradiation of N,N′-dibronio-2,5-piperazinedione in dichloromethane in the presence of an alcohol induced alkoxybromination of cyclohexene to give trans-1-bromo-2-alkoxycyclohexane in a good yield. The reaction was thought to proceed through an ionic mechanism.
Halogen Atom Participation in Guiding the Stereochemical Outcomes of Acetal Substitution Reactions
作者:Krystyna M. Demkiw、Wouter A. Remmerswaal、Thomas Hansen、Gijsbert A. van der Marel、Jeroen D. C. Codée、K. A. Woerpel
DOI:10.1002/anie.202209401
日期:2022.10.17
Nucleophilic additions to α-haloacetals proceed via an oxocarbenium ion intermediate where the carbon-halogen bond can either adopt a pseudo-axial or a pseudo-equatorial position. trans-Selectivity is typically observed when a halogen atom is positioned at C-2 of an acetal because hyperconjugative interactions involving the pseudo-axial carbon-halogen bond stabilize the oxocarbenium ion intermediate