ORGN 574 |
Stereoselective synthesis of 4-bromo-4-alkenoic acids and 4-bromo-4,6-alkadienoic acids from 2-bromoallyl propanoates via Claisen rearrangement
| Paul Sampson and Yehor Novikov. Department of Chemistry, Kent State University, Kent, OH 44242 |
| The stereoselective synthesis of ω-carboxy bromoalkenes 3 and bromodienes 5 from bromoallylic alcohols 1 is described. These compounds are potentially useful building blocks for the stereoselective construction of highly substituted alkenes. Bromoallylic alcohols 1 are readily accessible from reaction of 1-bromo-1-lithioethene with various aldehydes and ketones. We now demonstrate that propanoate esters 2 derived from 1 are useful substrates for Claisen rearrangement chemistry. Various enolate or silyl ketene acetal derivatives of 2 afford 4-bromo-4-alkenoic acids 3, with the yield depending heavily on the enolization conditions employed. Claisen rearrangement reactions were also performed using 2-bromo-1,4-pentadien-3-yl propanoates 4. Depending on the reaction conditions, some 4-bromo-4,6-alkadienoic acids (e.g. 5, R=Me) could be prepared in good yield and with high levels of chemo- and stereoselectivity. 
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New Reactions, Methodology, Heterocycles, Aromatics
8:00 PM-10:00 PM, Wednesday, August 25, 2004 Pennsylvania Convention Center -- Hall D, Poster
Division of Organic Chemistry
The 228th ACS National Meeting, in Philadelphia, PA, August 22-26, 2004
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