Transition-state stabilization by a secondary substrate-ligand interaction: a new design principle for highly efficient transition-metal catalysis.
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.
Smejkal
Tomás
T
Institut für Organische Chemie und Biochemie, Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, Albertstrasse 21, 79104 Freiburg, Germany.
Gribkov
Denis
D
Geier
Jens
J
Keller
Manfred
M
Breit
Bernhard
B
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*
D000475:Alkenes; D008024:Ligands; D009943:Organophosphorus Compounds; D028561:Transition Elements