A new approach to the air oxidation of alkenes employing metal nitro complexes as catalysts

Article abstract of DOI:10.1021/om00090a001

Alkenes are stoichiometrically and, in the presence of air, catalytically oxidized by cis-bis(acetonitrile)chloronitropalladium(II) (1). Oxidation of monosubstituted terminal alkenes and trans-cyclooctene yields the corresponding ketone, oxidation of cyclopentene and cyclohexene the corresponding allyl alcohol, and oxidation of bicyclic alkenes the corresponding epoxide, each with good selectivity for the respective product. Other alkenes give varying mixtures of the above products together with, in some cases, the α,β-unsaturated ketone. Vinyl ethers yield the corresponding ester while (trimethylsilyl)ethylene yields (trimethylsilyl)acetaldehyde. The selectivities are rationalized on the basis of ease of β-hydrogen elimination in observed intermediate heterometallacyclopentane complexes 3 formed by nucleophilic attack of the nitro oxygen atom on the coordinated alkene in alkene nitro complexes 2. The general role of metallacycles in metal-mediated alkene oxidations and the advantages and disadvantages of intra- vs. intermolecular metal nitro catalyzed alkene oxidations are discussed.