Metallation of 2-(alkenyl)pyridines by rhodium(III)

Abstract

Metallation of 2-(CHR²CR¹)py (py = pyridine) occurs on reaction with [Rh₂X₆(PBuⁿ₃)₄] to give [[graphic omitted]R²CR¹)py}X₂(PBuⁿ₃)₂](R¹,R²= H or Me; R¹= H, R²= Ph or C₆H₄OMe-p; X = Br or Cl). The stereochemistry of these products has been established by n.m.r. measurements and the mechanism of these reactions is discussed. The reaction of [R[graphic omitted]HCH)py}Br₂(PBuⁿ₃)₂]. with the excess of HBr results in re-formation of [Rh₂Br₆(PBuⁿ₃)₄] whereas there is no reaction with an equimolar amount of HBr; an unusual substitution occurs on reaction with bromine to give [[graphic omitted]HCBr)py}Br₂(PBuⁿ₃)₂].