A chemoselective method for the carbonylation of allylic substrates CH2=CHCH2X (X= OAc, OC(O)CH2CN, OPh, OEt, OC(O)OPh, OC(O)OiBu, N(H)C(O)Ph, N(Ph)C(O)Ph, N(H)Boc, N(Ph)Boc, Ph, CO2Bn, CN), leading to alkyl succinates with preservation of the X group, under Pd(II)-catalyzed oxidative carbonylation conditions, has been developed. Our method shows a completely different inverse chemoselectivity with respect to the "classical" substitutive carbonylation of the allyl compounds, which is known to provide beta,gamma-unsaturated carbonyl derivatives through the formation of a p-allylpalladium intermediate. An accurate study, carried out using allyl acetate as model substrate, allowed to maximize the selectivity in the envisioned 2-CH2X substituted succinates. The best catalyst is generated in situ by mixing Pd(TFA) 2 (TFA= trifluoroacetate) and the N,N'-di(anthracen-9-yl)butane-2,3-diimine ligand. pBenzoquinone was used as oxidant in presence of benzyl alcohol, which acts as a nucleophile and as a solvent, under 4 bar of CO at 20 degrees C. A combined effect of the ligand and the nucleophile, rationalized through DFT calculations, has been observed both in promoting the bis-alkoxycarbonylation process and in preventing p-allylpalladium-mediated side reactions, allowing the attainment of succinate derivatives with moderate to good yields.

Combined Effect of Palladium Catalyst and the Alcohol to Promote the Uncommon Bis-Alkoxycarbonylation of Allylic Substrates

Tarroni, R;Carfagna, C
2022

Abstract

A chemoselective method for the carbonylation of allylic substrates CH2=CHCH2X (X= OAc, OC(O)CH2CN, OPh, OEt, OC(O)OPh, OC(O)OiBu, N(H)C(O)Ph, N(Ph)C(O)Ph, N(H)Boc, N(Ph)Boc, Ph, CO2Bn, CN), leading to alkyl succinates with preservation of the X group, under Pd(II)-catalyzed oxidative carbonylation conditions, has been developed. Our method shows a completely different inverse chemoselectivity with respect to the "classical" substitutive carbonylation of the allyl compounds, which is known to provide beta,gamma-unsaturated carbonyl derivatives through the formation of a p-allylpalladium intermediate. An accurate study, carried out using allyl acetate as model substrate, allowed to maximize the selectivity in the envisioned 2-CH2X substituted succinates. The best catalyst is generated in situ by mixing Pd(TFA) 2 (TFA= trifluoroacetate) and the N,N'-di(anthracen-9-yl)butane-2,3-diimine ligand. pBenzoquinone was used as oxidant in presence of benzyl alcohol, which acts as a nucleophile and as a solvent, under 4 bar of CO at 20 degrees C. A combined effect of the ligand and the nucleophile, rationalized through DFT calculations, has been observed both in promoting the bis-alkoxycarbonylation process and in preventing p-allylpalladium-mediated side reactions, allowing the attainment of succinate derivatives with moderate to good yields.
2022
Olivieri, D; Tarroni, R; Della Ca', N; Mancuso, R; Gabriele, B; Spadoni, G; Carfagna, C
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/900625
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