Reactions of free radicals with η³-allylpalladium(ii) complexes: phenyl and trityl radicals

Reactions of free radicals with η3-allylpalladium(II) complexes: cyclohexyl radicals

“…To extend our previous investigation of the reactions of palladium allyl complexes of the types A, B and C with phenyl and trityl radicals [14], we now report a study of the reactions of the same types of allyl palladium compounds with the cyclohexyl radical. Cobaloximes, RCo(DMG) 2 (L), generally have rather weak Co-C bonds which undergo homolytic cleavage on irradiation by visible light to form alkyl radicals R Å and the cobalt(II) compound Co(DMG) 2 (L).…”

“…In view of our earlier work in which it was found that attack by phenyl radicals on g 3 -allyl palladium compounds generally occurred at the metal rather than at the allylic ligand [14], we anticipated that cyclohexyl radicals would also add preferentially at the metal. What was very unclear was what would happen next.…”

“…2 H NMR spectrum showing the resonance at d 3.14 of CH 2 @CH-CHD-Ph, the product of the reaction of (g 3 -1-phenylallyl)Pd(PPh 3 )Cl with (2,2,6,6-D 4 -c-hex)Co(DMG) 2 (py). [14]. Thus many of the reactions carried out here involved mixtures of A and PPh 3 , although in some cases preformed PPh 3 complexes were used.…”

“…We have earlier communicated some of our initial finding on this chemistry [16] and have reported in detail the chemistry of allyl-palladium compounds with phenyl and trityl radicals [14]. We now discuss an investigation of the analogous chemistry with cyclohexyl radicals, finding significant differences in reaction pathways.…”

“…We found [14] that compounds of the types (g 3 -allyl)PdCl(PPh 3 ) and [(g 3 -allyl)Pd(PPh 3 ) 2 ]Cl react readily with phenyl and trityl radicals in benzene at 60°C, the products being the palladium phenyl compounds, [PdPhCl(PPh 3 )] 2 and trans-PdPhCl(PPh 3 ) 2 , respectively, and 4,4,4-triphenyl-1-butene. In contrast, [(g 3 -allyl)-PdCl] 2 reacts with phenyl and trityl radicals under the same conditions to form palladium metal, trityl chloride and 3-phenylpropene, which is subsequently catalytically isomerized to 1-phenylpropene.…”