Insertion of 1,2-disubstituted alkynes into [Pd(CH3)(CO)(BIOX)]+[B{3,5-(CF3)2C6H3}4]− (1), where BIOX=(4S,4′S)-(−)-4,4′,5,5′-tetrahydro-4,4′-bis(1-methylethyl)-2,2′-bioxazole, leads to the formation of five-membered palladacycles, which, by reaction with carbon monoxide, produce a mixture of two diastereomeric forms of a palladium complex containing an η3-allylic γ-lactone ligand. On leaving the mixture in solution, one isomer was converted into the other, reaching a diastereomeric excess of up to 94 %. The steric and electronic factors responsible for the epimerization process were investigated by theoretical methods. Cleavage of the η3-allyl[BOND]palladium bond by nucleophiles allowed highly substituted chiral butenolides to be synthesized in good enantiomeric excess.
CARFAGNA C, GATTI G., MOSCA L., PAOLI P., GUERRI A. (2005). Stereocontrol in Alkyne Cyclocarbonylation Reactions promoted by a Bioxazoline Palladium(II) Complex. CHEMISTRY-A EUROPEAN JOURNAL, 11, 3268-3278 [10.1002/chem.200400326].
Stereocontrol in Alkyne Cyclocarbonylation Reactions promoted by a Bioxazoline Palladium(II) Complex
CARFAGNA, CARLA;
2005
Abstract
Insertion of 1,2-disubstituted alkynes into [Pd(CH3)(CO)(BIOX)]+[B{3,5-(CF3)2C6H3}4]− (1), where BIOX=(4S,4′S)-(−)-4,4′,5,5′-tetrahydro-4,4′-bis(1-methylethyl)-2,2′-bioxazole, leads to the formation of five-membered palladacycles, which, by reaction with carbon monoxide, produce a mixture of two diastereomeric forms of a palladium complex containing an η3-allylic γ-lactone ligand. On leaving the mixture in solution, one isomer was converted into the other, reaching a diastereomeric excess of up to 94 %. The steric and electronic factors responsible for the epimerization process were investigated by theoretical methods. Cleavage of the η3-allyl[BOND]palladium bond by nucleophiles allowed highly substituted chiral butenolides to be synthesized in good enantiomeric excess.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
