The syn/anti-dichotomy in the palladium-catalyzed addition of nucleophiles to alkenes.
In this review the stereochemistry of palladium-catalyzed addition of nucleophiles to alkenes is discussed, and examples of these reactions in organic synthesis are given. Most of the reactions discussed involve oxygen and nitrogen nucleophiles; the Wacker oxidation of ethylene has been reviewed in detail. An anti-hydroxypalladation in the Wacker oxidation has strong support from both experimental and computational studies. From the reviewed material it is clear that anti-addition of oxygen and nitrogen nucleophiles is strongly favored in intermolecular addition to olefin-palladium complexes even if the nucleophile is coordinated to the metal. On the other hand, syn-addition is common in the case of intramolecular oxy- and amidopalladation as a result of the initial coordination of the internal nucleophile to the metal.
Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 10691 Stockholm (Sweden), Fax: (+46) 8-154-908; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Prague 6 (Czech Republic); Department of Organic Chemistry, Charles University, Hlavova 8, 12843 Prague 2 (Czech Republic). pavel@organ.su.se, kocovsky@uochb.cas.cz.
Pavel
P
Kočovský
Jan-E
JE
Bäckvall
alkenes; catalysis; nucleophilic addition; palladium; stereochemistry