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A case study of proton shuttling in palladium catalysis.

ABSTRACT: The mechanism of alkynoic acid cycloisomerization with SCS indenediide Pd pincer complexes has been investigated experimentally and computationally. These studies confirmed the cooperation between the Pd center and the backbone of the pincer ligand, and revealed the involvement of a second molecule of substrate. It acts as a proton shuttle in the activation of the acid, it directs the nucleophilic attack of the carboxylic acid on the ?-coordinated alkyne and it relays the protonolysis of the resulting vinyl Pd species. A variety of H-bond donors have been evaluated as external additives, and polyols featuring proximal hydroxyl groups, in particular catechol derivatives, led to significant catalytic enhancement. The impact of 4-nitrocatechol and 1,2,3-benzenetriol is particularly striking on challenging substrates such as internal 4- and 5-alkynoic acids. Endo/exo selectivities up to 7.3/1 and 60-fold increase in reactivity were achieved.

SUBMITTER: Monot J

PROVIDER: S-EPMC5968755 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature

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A case study of proton shuttling in palladium catalysis.

Monot Julien J Brunel Paul P Kefalidis Christos E CE Espinosa-Jalapa Noel Ángel NÁ Maron Laurent L Martin-Vaca Blanca B Bourissou Didier D

Chemical science 20151207 3

The mechanism of alkynoic acid cycloisomerization with SCS indenediide Pd pincer complexes has been investigated experimentally and computationally. These studies confirmed the cooperation between the Pd center and the backbone of the pincer ligand, and revealed the involvement of a second molecule of substrate. It acts as a proton shuttle in the activation of the acid, it directs the nucleophilic attack of the carboxylic acid on the π-coordinated alkyne and it relays the protonolysis of the res ...[more]

PMID: 29899945

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