ORGN 8 |
| Incorporating the allene ether function into substrates for the Nazarov reaction leads to very rapid cyclization. There are probably two reasons for this, first, the small steric requirement of the sp-hybridized allene carbon atom, and second, polarization of the alkene through electron donation by the enol ether oxygen atom. The preparation of allene ethers is straightforward, however, the functionality is labile. An alternative strategy for using allene ethers in Nazarov cyclizations is to form the functionality in situ. This approach to the Nazarov can be adapted to the interrupted version, in which the reaction is terminated by trapping the intermediate cation with a suitable nucleophile.
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Allenes in Synthesis
8:00 AM-12:00 PM, Sunday, 26 March 2006 Georgia World Congress Center -- C303/304/305, Oral
Division of Organic Chemistry |