Catalysis by palladium salts

摘要: Abstract The carboxylation with CO of C-H bonds pseudo-aromatic systems such as furan and thiophene, mediated by palladium acetate, can be carried out in acetic acid or methanol solvent under 1 atm at low temperatures. Sodium acetate is an important cocatalyst. reaction highly regioselective, producing only the mixed anhydride between 2-furan 2-thiophene carboxylic acid. Working solvent, final products are corresponding methyl esters; however this main product, i.e. ester acid, contamined small amounts several byproducts. Yields increased respect to either addition excess mercury(II) cocatalyst carrying a two-step process. first step formation situ organomercury organothallium derivatives, using Hg(O2CMe)2, HgCl2 Tl(O2CMe)3, followed second step, oxidative carbonylation, acetate. sometimes higher than 100% achieved, maintaining same high regioselectivity ring substitution. By working pseudo-catalytic conditions (meaning presence oxidant Cu(II) acetate) we could not achieve yields reported other authors pressure; addition, negatively affected.