Stereoselective palladium-catalyzed carbocyclization ...
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Citation
| Title | Stereoselective palladium-catalyzed carbocyclization of allenic allylic carboxylates |
| Author(s) | J. Franzen, J. Lofstedt, J. Falk, J. Backvall |
| Journal | Journal of the American Chemical Society |
| Date | 2003 |
| Volume | 125 |
| Issue | 46 |
| Start page | 14140 |
| End page | 14148 |
| Abstract | Palladium(0)-catalyzed reaction of allene-substituted allylic carboxylates 3-8 employing 2-5 mol % of Pd(dba)(2) in refluxing toluene leads to the carbocyclization and elimination of carboxylic acid to give bicyclo[4.3.0]nonadiene and bicyclo[5.3.0]decadiene derivatives (12-17). The carbon-carbon bond formation is stereospecific, occurring syn with respect to the leaving group. Addition of maleic anhydride as a ligand to the above-mentioned procedures changed the outcome of the reaction, and under these conditions 3-5 afforded cycloisomerized products 21-23. The experimental results are consistent with a mechanism involving oxidative addition of the allylic carboxylate to Pd(0) to give an electron-deficient (pi-allyl)palladium intermediate, followed by nucleophilic attack by the allene on the face of the pi-allyl opposite to that of the palladium atom. Furthermore, it was found that the Pd(dba)(2)-catalyzed cyclization of the trans-cycloheptene derivative (trans-8) can be directed to give either the trans-fused (trans-17) or the cis-fused (cis-17) ring system by altering the solvent. The former reaction proceeds via a nucleophilic trans-allene attack on the (pi-allyl)palladium intermediate, whereas the latter involves a syn-allene insertion into the allyl-Pd bond of the same intermediate. The products from the carbocylization undergo stereoselective Diels-Alder reactions to give stereodefined polycyclic systems in high yields. |
| DOI | 10.1021/ja037398u |
| ISSN | 0002-7863 |
Using APA 6th Edition citation style.
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