Application of O2-DMSO as Reoxidant in the Pd(II)-Catalyzed 1,4-Oxidation of 5-Substituted 1,3-Cyclohexadienes.
作者:Magnus Rönn、Pher G. Andersson、Jan-E. Bäckvall、Markku Ahlgrén、Ward T. Robinson、Bryan R. Wood、Ward T. Robinson、Björn O. Roos、Claire Vallance、Bryan R. Wood
DOI:10.3891/acta.chem.scand.51-0773
日期:——
Palladium-catalyzed oxidation of 5-substituted 1,3-cyclohexadienes carrying a nucleophilic group in the side chain employing O-2-DMSO as the oxidant gave cyclization via 1,4-addition to the 1,3-diene. The nucleophilic groups employed were tosylamido and carboxy. In the reaction Pd-II is most likely reduced to colloidal Pd-0 which is subsequently reoxidized by O-2. The solvent DMSO prevents precipitation of metallic palladium by coordination to the colloidal particles. The stereochemistry of the palladium-catalyzed intramolecular 1,4-oxidation was controlled to some extent by the nature of the external nucleophile. Thus, in the intramolecular 1,4-oxyacyloxylation of 1 (hydroxy as nucleophile in the side chain) it was possible to direct the 1,4-addition towards cis or trans stereochemistry by variation of the external carboxylate nucleophile.