Mechanism of Palladium-Catalyzed Diene Cyclization/Hydrosilylation:  Direct Observation of Intramolecular Carbometalation

• Published in: Journal of the American Chemical Society Vol. 126; no. 20; pp. 6332 - 6346
• Main Authors: Perch, Nicholas S, Widenhoefer, Ross A
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 26.05.2004; Amer Chemical Soc
• Subjects: Alkenes - chemical synthesis; Catalysis; Chelating Agents - chemistry; Chemistry; Chemistry, Multidisciplinary; Cyclization; Exact sciences and technology; Indicators and Reagents; Kinetics; Kinetics and mechanisms; Magnetic Resonance Spectroscopy; Metals - chemistry; Organic chemistry; Palladium - chemistry; Physical Sciences; Reactivity and mechanisms; Science & Technology; Silanes - chemical synthesis; Silanes - chemistry; ALTERNATING COPOLYMERIZATION; CROSS-COUPLING REACTION; BIS-DIENES; COMPLEXES; MIGRATORY INSERTION REACTIONS; POLYMERIZATION; MEDIATED TETRAENE CARBOCYCLIZATIONS; OLEFIN; BETA-METHYL ELIMINATION; ALKYL ETHYLENE; Catalytic reaction; Palladium Complexes; Catalyst selectivity; Silicon Organic compounds; Organic silane; Hydrosilylation; NMR spectrometry; Transition metal Complexes; Complex catalyst; Dienic compound; Experimental study; Kinetic isotope effect; Cyclization; Reaction mechanism; Platinoid Complexes; Kinetic parameter; Rate constant; Catalyst activity
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja049806f

The results of kinetic, deuterium-labeling, and low-temperature NMR studies have established a mechanism for the palladium-catalyzed cyclization/hydrosilylation of dimethyl diallylmalonate (1) with triethylsilane involving rapid, irreversible conversion of the palladium silyl complex [(phen)Pd(SiEt3)(NCAr)]+ [BAr4]- [Ar = 3,5-C6H3(CF3)2] (4b) and 1 to the palladium 5-hexenyl chelate complex {(phen)Pd[η1,η2-CH(CH2SiEt3)CH2C(CO2Me)2CH2CHCH2]}+ [BAr4]- (5), followed by intramolecular carbometalation of 5 to form the palladium cyclopentylmethyl complex [BAr4]- (6), and associative silylation of 6 to release 3 and regenerate 4b.