Umpolung of the Allylpalladium Reactivity: Mechanism and Regioselectivity of the Electrophilic Attack on Bis-Allylpalladium Complexes Formed in Palladium-Catalyzed Transformations
✍ Scribed by Kálmán J. Szabó
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 221 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
The structure and reactivity of various bis-allylpalladium complexes occurring as catalytic intermediates in important synthetic transformations have been studied by applying density functional theory at the B3PW91(DZ P) level. It was found that h 1 ,h 3 coordinated bis-allylpalladium complexes are readily formed from the corresponding h 3 ,h 3 complexes, especially in the presence of p-acceptor phosphine ligands.
The theoretical calculations indicate d s 3 p* type hyperconjugative interactions occurring in the h 1 -coordinated allyl moiety of the h 1 ,h 3 coordinated complexes. These hyperconjugative in-teractions influence the structure of the complexes and dramatically increase the reactivity of the double bond in the h 1moiety. The DFT results indicate a remarkably low activation barrier for the electrophilic attack on the h 1 -allyl functionality. In bridged h 1 ,h 3 complexes, the electrophilic attack occurs with a very high regioselectivity, which can be explained on the basis of d ± p type hyperconjugative interactions.