Oxidation of Cycloalkenes and Methylenecycloalkanes by Palladium(II) Complexes. Part 2. NMR Study on the Mechanism of the Ring Expansion of Methylenecyclobutane
Journal of Molecular Catalysis (Continued after 1994 as Journal of Molecular Catalysis A: Chemical and Journal of Molecular Catalysis B: Enzymatic)
||cycloalkene oxidation, methylenecyclobutane, oxidation, palladium
Boreskov Institute of Catalysis
The reaction of methylenecyclobutane (1) with bis(acetonitrile)chloronitropalladium(II) in methylene chloride yields cyclopentanone. Two intermediates - π-olefin complex of palladium and product of β-nitritopalladation of 1 in a Markovnikov fashion - are observed by 1H and 13C NMR. Palladium-catalyzed ring expansion of 1 is suggested to involve heterolysis of the palladium-carbon bond and rearrangement of the resulting cyclobutyl to cyclopentyl cations. The selective formation of ring-expanded and ring-contracted carbonyl products from methylenecyclobutane and
1-methyleyclobutene, respectively, is discussed in terms of proposed mechanism.