Stereocontrol in Alkyne Cyclocarbonylation Reactions Promoted by a Bioxazoline Palladium(ii) Complex

✍ Scribed by Carla Carfagna; Giuseppe Gatti; Luca Mosca; Paola Paoli; Annalisa Guerri

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 357 KB
• Volume: 11
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200400326

✦ Synopsis

Abstract

Insertion of 1,2‐disubstituted alkynes into [Pd(CH~3~)(CO)(BIOX)]^+^[B{3,5‐(CF~3~)~2~C~6~H~3~}~4~]^−^ (1), where BIOX=(4__S__,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 η^3^‐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 η^3^‐allylpalladium bond by nucleophiles allowed highly substituted chiral butenolides to be synthesized in good enantiomeric excess.