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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).
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The Higher Propensity of Pd-SiHEt 2 + over Pd-SiMe 2 Et + to Transfer Silylium to Silyl Ether Intermediates Explains Divergent Products in Ketone Hydrosilylation Catalysis
The catalytic use of silylpalladium cations has been developed for the hydrosilylation of ketones. Product outcome was heavily influenced by hydrosilane identity with tertiary silanes providing silyl ethers and secondary silanes, alkanes. Stoichiometric studies suggest a key differentiating feature is the ability to transfer silylium from XantPhosPd-SiR3+ to silyl ether intermediates in the case of secondary silanes but not tertiary. Formation of a bimetallic Pd species during catalysis with secondary silanes points to silylpalladium cations behaving as a source of both electrophilic silylium ions and nucleophilic Pd(0).
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- Award ID(s):
- 2154432
- PAR ID:
- 10514040
- Publisher / Repository:
- Organometallics
- Date Published:
- Journal Name:
- Organometallics
- Volume:
- 43
- Issue:
- 11
- ISSN:
- 0276-7333
- Page Range / eLocation ID:
- 1256 to 1263
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.organomet.4c00104
