<i>Ortho</i>Substituents Direct Regioselective Addition of Tributyltin Hydride to Unsymmetrical Diaryl (or Heteroaryl) Alkynes: An Efficient Route to Stannylated Stilbene Derivatives

Abstract

An unprecedented ortho-directing effect (ODE) in diaryl alkynes 1 (R=electron-withdrawing or electron-donating group) promotes regioselective addition of tributyltin hydride to the triple bond and afforded efficiently stannylated unsymmetrical 1,2-diaryl olefins 2. The precise contributions of steric, electronic, and coordinative factors, which control this regioselectivity are highlighted. The results are rationalized in terms of electronic polarization across the alkyne bond, induced by the ortho substituent whatever its electronic nature.