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Structural and Mechanistic Studies on the Activation and Propagation of a Cationic Allylpalladium Procatalyst in 1,6-Diene Cycloisomerization

โœ Scribed by Katharine L. Bray; Jonathan P. H. Charmant; Ian J. S. Fairlamb; Guy C. Lloyd-Jones

Book ID
101372376
Publisher
John Wiley and Sons
Year
2001
Tongue
English
Weight
207 KB
Volume
7
Category
Article
ISSN
0947-6539

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โœฆ Synopsis

Pd(h 3 -C 3 H 5 )(MeCN) 2 ]OTf acts as an efficient procatalyst for the cycloisomerisation of dimethyl hept-1,6dienyl-4,4-dicarboxylate (1 a) in CHCl 3 . The reaction displays a pronounced and variable induction period and gives dimethyl 3-methylene-4-methylcyclopentane-1,1-dicarboxylate (2 a) as the kinetic product. The thermodynamically more favourable tri-and tetra-substituted alkenes dimethyl 3,4-dimethylcylopent-2-ene-1,1-dicarboxylate (3 a) and dimethyl 3,4-dimethylcylopent-3-ene-1,1-dicarboxylate (4 a) are also generated directly (3 a) or by isomerisation (3 a and 4 a) of 2 a. The mechanism of procatalyst activation and the ensuing cycloisomerisation reaction was investigated by NMR spectroscopy ( 1 H, 2 H, 13 of 15 a and the requirement for traces of water for b-H elimination accounts for variability in the induction period when [Pd(h 3 -C 3 H 5 )(MeCN) 2 ]OTf is employed as procatalyst.

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