title: Transition-state stabilization by a secondary substrate-ligand interaction: a new design principle for highly efficient transition-metal catalysis.
abstract: A library of monodentate phosphane ligands, each bearing a guanidine receptor unit for carboxylates, was designed. Screening of the library gave some excellent catalysts for regioselective hydroformylation of beta,gamma-unsaturated carboxylic acids. A terminal alkene, but-3-enoic acid, was hydroformylated with a linear/branched (l/b) regioselectivity up to 41. An internal alkene, pent-3-enoic acid was hydroformylated with regioselectivity up to 18:1. Further substrate selectivity (e.g., acid vs. methyl ester) and reaction site selectivity (monofunctionalization of 2-vinylhept-2-enoic acid) were also achieved. Exploration of the structure-activity relationship and a practical and theoretical mechanistic study gave us an insight into the nature of the supramolecular guanidinium-carboxylate interaction within the catalytic system. This allowed us to identify a selective transition-state stabilization by a secondary substrate-ligand interaction as the basis for catalyst activity and selectivity.
authors.affiliation: Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg, Germany.
authors.forename: Tomás
authors.initials: T
authors.lastname: Smejkal
authors.forename: Denis
authors.initials: D
authors.lastname: Gribkov
authors.forename: Jens
authors.initials: J
authors.lastname: Geier
authors.forename: Manfred
authors.initials: M
authors.lastname: Keller
authors.forename: Bernhard
authors.initials: B
authors.lastname: Breit
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D008024:Ligands; D015394:Molecular Structure; D009943:Organophosphorus Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D000475:Alkenes; D008024:Ligands; D009943:Organophosphorus Compounds; D028561:Transition Elements