Reactions of Phenyl(styryl)iodonium Tetrafluoroborate with Halide Ions

Article abstract of DOI:10.1246/bcsj.71.1915

Reactions of (E)-phenyl(styryl)iodonium tetrafluoroborate with chloride, bromide, and iodide ions are examined under various conditions. The products are those of substitution and elimination, involving (Z)-1-halo-2-phenylethene (2), phenylacetylene (3), and iodobenzene as main products as well as minor products of (E)-2 and 1-halo-1-phenylethene. Results of product analysis, UV absorption spectroscopy, and kinetic measurements are consistent with major pathways involving pre-equilibrium formation of halo-λ³-iodane and iodate intermediates, leading to the in-plane vinylic S_N2 substitution to (Z)-2 and the intramolecular β-elimination to 3. The minor retained product (E)-2 is concluded to be formed through the vinylenebenzenium ion intermediate in 2,2,2-trifluoroethanol through the ligand coupling within the λ³iodane intermediate in acetonitrile. 1-Bromo-1-phenylethene is considered to be derived from 3 by reaction with HBr formed during the reaction.