869966-73-4Relevant academic research and scientific papers
Oxidative coupling of activated alkynes with palladium(0) olefin complexes: Side production of the highly symmetric hexamethyl mellitate species under mild conditions at low alkyne/complex molar ratios
Canovese, Luciano,Visentin, Fabiano,Chessa, Gavino,Santo, Claudio,Levi, Carlo,Uguagliati, Paolo
, p. 388 - 390 (2008/10/09)
The reactions of oxidative coupling of dimethylacetylene dicarboxylate (DMA) with palladium (0) olefin complexes bearing a pyridylthioether as ancillary ligand give rise to the corresponding palladacyclopentadienyl complexes as the main product and in some cases to the highly symmetric hexamethyl mellitate molecule, especially when a low alkyne(DMA)/complex ratio is employed. A plausible mechanism based on several pieces of experimental evidence is proposed, and the most effective complexes promoting the hexamethyl mellitate synthesis were identified.
Attack of substituted alkynes on olefin palladium(O) derivatives of pyridylthioethers. The first kinetic study on the mechanism of formation of palladacyclopentadiene complexes
Canovese, Luciano,Visentin, Fabiano,Chessa, Gavino,Uguagliati, Paolo,Levi, Carlo,Dolmella, Alessandro
, p. 5537 - 5548 (2008/10/09)
The formation of metallacyclopentadienyl derivatives was studied under controlled conditions, and the kinetics and mechanism of reactions between pyridylthioether olefin Pd(0) substrates and substituted alkynes of the type ZC=CZ (Z = COOMe, COOEt, COOt-Bu) leading to the corresponding palladacyclopentadienyl species were systematically investigated. In the case of less hindered ancillary ligands the attack of the alkyne forming a reactive monoalkyne intermediate was found to be the rate-determining step. In this respect the rates of reaction were discussed in terms of the substituent-induced basicity-of sulfur and nitrogen of the ancillary ligands. The associative nature of the attack was unequivocally established, and the formation of a transition state bearing a monodentate ancillary ligand was proposed. In the case of more hindered ancillary ligands a partially stabilized monoalkyne intermediate is formed irrespective of the olefin in the starting complex, and this species strongly influences the reaction progress. Formation of hexamethylmellitate under mild conditions is also observed.
