4538-09-4Relevant articles and documents
Why platinum catalysts involving ligands with large bite angle are so efficient in the allylation of amines: Design of a highly active catalyst and comprehensive experimental and DFT study
Mora, Guilhem,Piechaczyk, Olivier,Houdard, Romaric,Mezailles, Nicolas,Le Goff, Xavier-Frederic,Le Floch, Pascal
, p. 10047 - 10057 (2008)
The platinum-catalyzed allylation of amines with allyl alcohols was studied experimentally and theoretically. The complexes [Pt(η3-allyl)- (dppe)]OTf (2) and [Pt(η3-allyl)(DPP-Xantphos)]PF6 (5) were synthesized and structurally characterized, and their reactivity toward amines was explored. The bicyclic aminopropyl complex [Pt(CH2CH 2CH2NHBn-κ-C,N)-(dppe)]OTf (3) was obtained from the reaction of complex 2 with an excess of benzylamine, and this complex was shown to be a deactivated form of catalyst 2. On the other hand, reaction of complex 5 with benzylamine and allyl alcohol led to formation of the 16-VE platinum(0) complex [P(η2-C3H3OH)-(DPP-Xantphos)] (7), which was structurally characterized and appears to be a catalytic intermediate. A DFT study showed that the mechanism of the platinum-catalyzed allylation of amines with allyl alcohols differs from the palladium-catalyzed process, since it involves an associative ligand-exchange step involving formation of a tetracoordinate 18-VE complex. This DFT study also revealed that ligands with large bite angles disfavor the formation of platinum hydride complexes and therefore the formation of a bicyclic aminopropyl complex, which is a thermodynamic sink. Finally, a combination of 5 and a proton source was shown to efficiently catalyze the allylation of a broad variety of amines with allyl alcohols under mild conditions.
