Silver carboxylate salts are widely used as additives in palladium-catalyzed C−H functionalization reactions. However, the role of these silver additives is often not fully understood. This paper describes an investigation of the role of AgOPiv in the stoichiometric activation of C 6 F 5 H at a well-defined Pd II complex as well as in the Pd II -catalyzed oxidative dimerization of 2-alkylthiophenes. Both in situ NMR spectroscopy and H/D exchange studies of the reactions of C 6 F 5 H implicate a role for AgOPiv in the C−H cleavage event, generating Ag−C 6 F 5 as an intermediate. The catalytic studies show similar trends despite the different conditions and substrates, suggesting that AgOPiv promotes a similar metalation of the thiophene in the catalytic transformations. This proposal is supported by DFT calculations, which show energetically feasible pathways for concerted metalation−deprotonation of both 2methylthiophene and pentafluorobenzene at [Ag(OPiv)] 2 . These studies suggest that initial metalation of C−H substrates at Ag I carboxylates should be considered as a plausible pathway in C−H functionalization reactions involving mixtures of Ag and Pd salts.
This article describes the high-yielding and selective oxidatively induced formation of ethane from mono-methyl palladium complexes. Mechanistic details of this reaction have been explored via both experiment and computation. On the basis of these studies, a mechanism involving methyl group transmetalation between Pd(II) and Pd(IV) interediates is proposed.
A concise total synthesis of the Lycopodium alkaloid lycopladine A (1) is described that features sequential conjugate addition and enolate arylation reactions to construct the tricyclic core in two steps.
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