Ortho-vinylation Reaction of Phenols with Ethylene

Phenols were vinylated at the ortho-position with ethylene in the presence of SnCl₄-Bu₄N reagent. The reaction was applicable to phenols possessing either electron-donating or electron-withdrawing group. 2,6-Divinylphenols were synthesized under mild conditions. Ab initio calculations of alkynyltin model compounds, HCequivCSnF₃ and HCequivCSnH₃ showed that the beta carbon atom was less negatively charged than the alpha carbon atom. In addition, the coefficients of pi^* orbitals of C-C triple bond were larger at the Beta carbon atom. These results rationalized the mechanism of the ortho-vinylation reactions.