Synthesis and Characterization of β-Haloalkenyl-λ<sup>3</sup>-bromanes: Stereoselective Markovnikov Addition of Difluoro(aryl)-λ<sup>3</sup>-bromane to Terminal Acetylenes
作者:Masahito Ochiai、Yoshio Nishi、Takeshi Mori、Norihiro Tada、Takashi Suefuji、Hermann J. Frohn
DOI:10.1021/ja051690f
日期:2005.8.1
Reported here for the first time are the synthesis, isolation, and characterization of hypervalent beta-haloalkenyl-lambda3-bromanes. Exposure of terminal alkynes to p-trifluoromethylphenyl(difluoro)-lambda3-bromane activated by BF3-i-Pr2O resulted in fluoro-lambda3-bromanation of the triple bonds in a Markovnikov fashion, yielding (E)-beta-fluoroalkenyl-lambda3-bromanes stereoselectively in good yields. 5-Chloro-1-pentynes undergo domino lambda3-bromanation-chlorine shift-fluorination or lambda3-bromanation-chlorine shift-alkyl shift-fluorination reaction, depending on the substituents and afford (E)-beta-chloroalkenyl-lambda3-bromanes stereoselectively in high yields. The beta-chloroalkenyl-lambda3-bromanes contain three kinds of halogen atoms, F, Cl, and Br, in the molecule.