H2TPP Organocatalysis in Mild and Highly Regioselective Ring Opening of Epoxides to Halo Alcohols by Means of Halogen Elements

摘要

We found that elemental iodine and bromine are converted to trihalide nucleophiles (triiodine and tribromide anion, respectively) in the presence of catalytic amounts of meso-tetraphenylporphyrins (H₂TPP). Therefore a highly regioselective method for the synthesis of b-haloalcohols through direct ring opening of epoxides with elemental iodine and bromine in the presence of H₂TPPs as new catalysts is described. At room temperature a series of epoxide derivatives were converted into the corresponding halohydrins resulting from an attack of trihalide species anion atoms at the less substituted carbon atom. This method occurs under neutral and mild conditions with high yields in various aprotic solvents, even when sensitive functional groups are present.