- Oxidant speciation and anionic ligand effects in the gold-catalyzed oxidative coupling of arenes and alkynes
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The mechanism of the gold-catalyzed oxidative cross-coupling of arenes and alkynes has been studied in detail combining stoichiometric experiments with putative reaction intermediates and DFT calculations. Our data suggest that ligand exchange between the alkyne, the Au(i)-catalyst and the hypervalent iodine reagent is responsible for the formation of both an Au(i)-acetylide complex and a more reactive "non-symmetric" I(iii) oxidant responsible for the crucial Au(i)/Au(iii) turnover. Further, the reactivity of the in situ generated Au(iii)-acetylide complex is governed by the nature of the anionic ligands transferred by the I(iii) oxidant: while halogen ligands remain unreactive, acetato ligands are efficiently displaced by the arene to yield the observed Csp2-Csp cross-coupling products through an irreversible reductive elimination step. Finally, the nature of competitive processes and catalyst deactivation pathways has also been unraveled. This detailed investigation provides insights not only on the specific features of the species involved in oxidative gold-catalyzed cross couplings but also highlights the importance of both ancillary and anionic ligands in the reactivity of the key Au(iii) intermediates.
- Hofer, Manuel,De Haro, Teresa,Gómez-Bengoa, Enrique,Genoux, Alexandre,Nevado, Cristina
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p. 8411 - 8420
(2019/09/30)
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- Hypercoordinated gold(I) compounds 5. Reactions of complex salts of monovalent gold with bimetallic Li,K derivatives of o-cresol and o-thiophenol
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The reaction of [O(AuPPh3)3]+BF4- with a Li,K derivative of o-cresol followed by the interaction of the reaction product with CO2 gave (triphenylphosphine)gold acetate. The reaction of ClAuPPh3 with o-LiC6H4SLi afforded (triphenylphosphine)gold thiophenoxide. According to the data of X-ray structural analysis, the latter occurs as a dimer formed through an intermolecular secondary Au...Au bond. The reaction of this complex with diazomethane was accompanied by insertion of carbene into the Au - S bond to form a new gold complex, PhSCH2AuPPh3. The reactions with PPh3Au+BF4- or HBF4 yielded a new tetranuclear gold thiocluster, {[PhS(AuPPh3)2]2+(BF4 -)}2, which involves Au...Au bonds that differ in strength. The structures of the compounds obtained were established by X-ray structural analysis, 1H and 31P NMR spectroscopy, and FAB mass spectrometry.
- Baukova,Kuz'mina,Churakov,Oleinikova,Petrovskii
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p. 343 - 348
(2007/10/03)
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