ESI-MS Studies in Palladium-Catalyzed Allylic Substitution Reactions

ESI-MS Studies in Palladium-Catalyzed Allylic Substitution Reactions 

In a first stage, a 1 2 mixture of [(7t-allyl)PdCl]2 and 56 revealed a peak corresponding to the intermediate I79b, which again showed the coordination of the palladium atom with the hydrophilic ligand. This complex had an allyl moiety coordinated to the metal in an or coordination mode (Entry 6). No new peaks were observed when the allylic acetate 51b was added to the above mixture. However, when nucleophile 54 was added, two new peaks were detected after 1 h. at 50 °C (i) a 7t-allyl palladium complex (I81b) and (ii) an intermediate 

The authors suggested that the real catalyst was the neutral intermediate I79b, detected as a cluster at m/z = 611, corresponding to I79b. The oxidative addition of ailylic acetate Sib to the above intermediate afforded the formation of a Pd(IV) ji-allyl complex 184, which was not detected directly by ESI-MS. However, the authors postulate that this complex may be related to intermediates I81b,I83 and 182, which were all observed in the ESI mass spectra. Reductive elimination from 184 and interaction with S4 close the catalytic cycle. 

The first step of the reaction generated a cationic Jt-allyl palladium complex 185/186 which was easily detectable by ESI-MS. Then, the nucleophile attack afforded the 

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S ESI-MS Studies in Palladium-Catalyzed Allylic Substitution Reactions 261 O O... 

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