- Radical-chain functionalisation at C-H centres using an O-oxiranylcarbinyl O-silyl ketene acetal
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A readily prepared O-oxiranylcarbinyl O-silyl ketene acetal has been used to bring about functionalisation at various types of saturated C-H group, through the intermediacy of an oxiranylcarbinyl radical that undergoes rapid ring opening to give a highly reactive allyloxyl radical.
- Cai, Yudong,Dang, Hai-Shan,Roberts, Brian P.
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- Combined Effect of Palladium Catalyst and the Alcohol to Promote the Uncommon Bis-Alkoxycarbonylation of Allylic Substrates
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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 β,γ-unsaturated carbonyl derivatives through the formation of a π-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. p-Benzoquinone 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 °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 π-allylpalladium-mediated side reactions, allowing the attainment of succinate derivatives with moderate to good yields.
- Olivieri, Diego,Tarroni, Riccardo,Della Ca', Nicola,Mancuso, Raffaella,Gabriele, Bartolo,Spadoni, Gilberto,Carfagna, Carla
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- Novel acyclic ligands. Part 1. Synthesis of some dicarboxamide derivatives
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The synthesis of three novel acyclic bis(amino-substituted amides), 3, 4 and 5, each of which possesses a bridging carbon atom carrying a suitable amino-bearing functionality, is described. These compounds may serve as contrast agents in magnetic resonance imaging.
- Elsworth, John F.,Msimang, Lorenzo N.,Jackson, Graham E.
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