Oxygen-Transfer Reactions Catalyzed by Nitropalladium(II) Complexes. Reactivity of Bis(μ-chloro)bishept-2-yl-C,N>dipalladium: Cleavage of the C-Pd Bond

Article abstract of DOI:10.1021/jo00386a006

The oxidation of various norbornene derivatives and several mono- and nonconjugated diolefines with the catalyst (CH3CN)2PdCl(NO2) (1) is described.In contrast with the results previously observed with Wacker-type catalysts (PdCl2-CuCl2), the epoxidation process is selective for the strained norbornene double bond with dienes 5 or 7.Methyl ketones such as 14, 16, 18, and 20 are obtained with unhindered terminal olefins (e.g., 20 from 19).The solution structure of bis(μ-chloro)bishept-2-yl-C,N>dipalladium (32) as analyzed by 1H and 13C NMR spectroscopy shows that there is a slight distortion of the palladacycle.The reactivity of isolated complex 32 has been studied.In aprotic solvents (benzene, toluene) and in the absence of any nucleophilic reagents, a pure oxygen-transfer reaction yielding epoxide 4 is the sole process.In the presence of nucleophiles or oxidants like CuCl2 or Pb(OAc)4 in protic or aprotic solvents (HOAc, CH2Cl2), the cleavage mode of the C-Pd bond is quite different.The formation of disubstituted norbornane derivatives 34 and 35 and nonrearranged products 36 and 37 are observed.The formation of various products from isolated complex 32 is discussed in terms of reaction mechanisms, particularly relative to the C-Pd bond reactivity.