Oxidative Addition of Allylic Carbonates to Palladium(0) Complexes: Reversibility and Isomerization

Abstract

The oxidative addition of a cyclic allylic carbonate to the palladium(0) complex generated from a [Pd(dba)2]+2 PPh3 mixture affords a cationic pi-allylpalladium(II) complex with the alkyl carbonate as the counter-anion. This reaction is reversible and proceeds with isomerization of the allylic carbonate at the allylic position. The equilibrium constant has been determined in DMF. The influence of the precursor of the palladium(0) is discussed.

Effect of the leaving group and the allylic structure on the kinetics and thermodynamics of the reaction of allylic carboxylates with palladium(0) complexes

“…After addition of the suitable amount of the allylic carboxylate at the desired temperature, the increase of the conductivity was recorded versus time up to the limiting value, according to the procedure reported in previous works. [2][3][4][5] …”

“…The reversibility of the reaction of a cyclic allylic carbonate has also been established with PPh 3 as well as an epimerization at the allylic position. 5 Consequently, in a palladium-catalyzed nucleophilic allylic substitution, the acetate or carbonate ions whose concentration increases as the catalytic reaction proceeds, may compete with poor or stabilized nucleophiles in the nucleophilic attack on cationic (η 3 -allyl)palladium(II) complexes, leading thus to scrambling in the allylic substrates. 5,6 This shows that acetate or carbonate ions are not only simple leaving groups as generally postulated, but that they may play an active role in the catalytic process.…”

Catalytic Domino Annulations through η3‐Allylpalladium Chemistry: A Never‐Ending Story

“…The expected mechanism (Scheme ) involves attack of the primary amine on the η 3 ‐allylpalladium intermediate A in turn generated by ionization of the bis‐electrophile by the in situ generated Pd(0) complex. Subsequent cyclization – rather than ionization – leads to an allylic 7‐membered carbamate, which undergoes a further ionization to generate the new η 3 ‐allylpalladium intermediate B .…”

Palladium-Catalyzed Methoxycarbonylation of 1,3-Butadiene: Catalysis and Mechanistic Studies

“…Encouraged by the work of Amatore et al, [24] we also tried to synthesize crotylpalladium complexes by oxidative addition of different crotyl esters, e.g., crotyl acetate, crotyl benzoate, crotyl 4-tert-butylbenzoate, to Pd(0) (Scheme 4). This strategy has the advantage to obtain directly palladium complexes having the same counterions compared to the intermediates of the catalytic cycle.…”