title: Investigating the nature of palladium chain-walking in the enantioselective redox-relay Heck reaction of alkenyl alcohols.
abstract: The mechanism of the redox-relay Heck reaction was investigated using deuterium-labeled substrates. Results support a pathway through a low energy palladium-alkyl intermediate that immediately precedes product formation, ruling out a tautomerization mechanism. DFT calculations of the relevant transition structures at the M06/LAN2DZ+f/6-31+G* level of theory show that the former pathway is favored by 5.8 kcal/mol. Palladium chain-walking toward the alcohol, following successive β-hydride eliminations and migratory insertions, is also supported in this study. The stereochemistry of deuterium labels is determined, lending support that the catalyst remains bound to the substrate during the relay process and that both cis- and trans-alkenes form from β-hydride elimination.
authors.affiliation: Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112, United States.
authors.forename: Margaret J
authors.initials: MJ
authors.lastname: Hilton
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Xu
authors.forename: Per-Ola
authors.initials: PO
authors.lastname: Norrby
authors.forename: Yun-Dong
authors.initials: YD
authors.lastname: Wu
authors.forename: Olaf
authors.initials: O
authors.lastname: Wiest
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Sigman
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism
chemical_list: D000438:Alcohols; D000475:Alkenes; D010165:Palladium