Heterolytic Cleavage of L_nPd-SiR₃⁺ Bonds Enable the Ring-Opening C-C Functionalization of Nonstrained Ethers

Silyl palladium cations (R₃P)₂Pd-SiR₃⁺ catalyze the ring opening, C-C bond forming, and functionalization of 5- and 6-membered cyclic allyl ethers with O-silyl nucleophiles. Conditions for high regio-control are achieved by adjustments in the phosphine electronics, with the identity of the 2-substituent also influencing the functionalization location in unsymmetrical furans. Allyl alcohols are obtained with a regio-preference for terminal addition with unsubstituted ethers with E-products being obtained with XantPhos and Z- with (4-CF₃-Ar)₃ ligation. Styrenes dominate with phenyl-substituted dihydrofurans, and for 2-alkyl-substituted, secondary alcohols result from an allyl migration pathway. Mechanistic studies demonstrate the feasibility of Pd-Si⁺ bonds to facilitate C-O activation to yield π-allyl intermediates, and for one substrate class to also sequence π-allyl migration prior to nucleophilic addition. DFT calculations demonstrated the viability of silylium-activated ether as a competent ligand for Pd(0).