Effects of stereochemistry and β-substituents on the rates of vinylic SN2 reaction of hypervalent vinyl(phenyl)-λ3-iodanes with tetrabutylammonium halides

Both stereoisomers of β-(2-phenylethoxy)vinyl-λ3-iodane and (Z)-β-aroyloxyvinyl-λ3-iodane were prepared stereoselectively. These substituted vinyl-λ3-iodanes undergo nucleophilic vinylic substitutions with n-Bu4NX (X=Cl, Br, I) under mild conditions, yielding vinyl halides. The observed inversion of configuration at the ipso vinylic carbon atom is compatible with a concerted vinylic SN2 mechanism. Kinetic measurements indicated that the rates for vinylic SN2 reaction of (Z)-vinyl-λ3-iodane are greater than those of the E-isomer, probably because of the higher ground state energy of the Z-isomer. Electronic effects of β-substituents of vinyl-λ3-iodanes in the vinylic SN2 reaction are also discussed.