Tailored quinones support high-turnover Pd catalysts for oxidative C-H arylation with O<sub>2</sub>.
basic_science · Level V
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- Record sourced from PubMed, PMID 33214286.
- Also identified by DOI 10.1126/science.abd1085 and PMC identifier 8081070.
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Abstract
Palladium(II)-catalyzed carbon-hydrogen (C-H) oxidation reactions could streamline the synthesis of pharmaceuticals, agrochemicals, and other complex organic molecules. Existing methods, however, commonly exhibit poor catalyst performance with high palladium (Pd) loading (e.g., 10 mole %) and a need for (super)stoichiometric quantities of undesirable oxidants, such as benzoquinone and silver(I) salts. The present study probes the mechanism of a representative Pd-catalyzed oxidative C-H arylation reaction and elucidates mechanistic features that undermine catalyst performance, including substrate-consuming side reactions and sequestration of the catalyst as an inactive species. Systematic tuning of the quinone cocatalyst overcomes these deleterious features. Use of 2,5-di-<i>tert</i>-butyl-<i>p</i>-benzoquinone enables efficient use of molecular oxygen as the oxidant, high reaction yields, and >1900 turnovers by the Pd catalyst.