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Publications (2)13.45 Total impact

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    ABSTRACT: The key step in the mechanism of the Palladium-catalyzed homocoupling of arylboronic acids ArB(OH)(2)(Ar = 4-Z-C(6)H(4) with Z = MeO, H, CN) in the presence of dioxygen, leading to symmetrical biaryls, has been elucidated by using density functional theory. In particular, by starting from the peroxo complex O(2)PdL(2)(L = PPh(3)), generated in the reaction of dioxygen with the Pd(0) catalyst, the fundamental role played by an intermediate formed by coordination of one oxygen atom of the peroxo complex to the oxophilic boron atom of the arylboronic acid has been pointed out. This adduct reacts with a second molecule of arylboronic acid to generate a cis-Ar-Pd(OOB(OH)(2))L(2) complex that can form the stable intermediate trans-Ar-Pd(OH)L(2) (experimentally characterized) through a sequence of hydrolysis and isomerization reactions. All theoretical insights are in agreement and do substantiate the experimentally postulated mechanism. Furthermore, direct comparison of experimental and computed spectroscopic parameters (here, (31)P chemical shifts) allows us to confirm the formation of the intermediate.
    The Journal of Physical Chemistry A 08/2008; 112(50):12896-903. · 2.77 Impact Factor
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    ABSTRACT: The mechanism of the palladium-catalyzed homocoupling of arylboronic acids ArB(OH)(2) (Ar = 4-Z-C(6)H(4) with Z = MeO, H, CN) in the presence of dioxygen, leading to symmetrical biaryls, has been fully elucidated. The peroxo complex (eta(2)-O(2))PdL(2) (L = PPh(3)), generated in the reaction of dioxygen with the Pd(0) catalyst, was found to play a crucial role. Indeed, it reacts with the arylboronic acid to generate an adduct (coordination of one oxygen atom of the peroxo complex to the oxophilic boron atom of the arylboronic acid) characterized by (31)P NMR spectroscopy and ab initio calculations. This adduct reacts with a second molecule of arylboronic acid to generate trans-ArPd(OH)L(2) complexes. A transmetalation by the arylboronic acid gives trans-ArPdArL(2) complexes. The biaryl is then released in a reductive elimination. This reaction is at the origin of the formation of biaryls as byproducts in palladium-catalyzed Suzuki-Miyaura reactions when they are not conducted under oxygen-free atmosphere.
    Journal of the American Chemical Society 06/2006; 128(21):6829-36. · 10.68 Impact Factor