PdCl2-promoted reactions of diaryl-substituted methylenecyclopropanes

Abstract

The PdCl₂-promoted reactions of methylenecyclopropanes (MCPs) 1 bearing diaryl substituents on the terminal double bond were carefully investigated. The solvents employed significantly affected the reaction outcomes. It was found that dimeric allylpalladium(II) complexes 2a–2f can be obtained as the sole products in acceptable to good yields under mild reaction conditions with THF as the solvent, while dimeric allylpalladium(II) complexes 2a–2f along with another type of dimeric allylpalladium(II) complexes 4a–4e can be obtained in good to high total yields if N,N-dimethylacetamide (DMAc) was used as the solvent. Moreover, using N,N-dimethylformamide (DMF) as the solvent in the presence of water, it was found that water can also participate in the reaction to form another type of dimeric allylpalladium(II) complex 6 as the minor product. All of these dimeric allylpalladium(II) complexes reported in the paper have been characterized by X-ray crystal structure diffraction.