ORGN 92 |
| Allylic boronates are important intermediates for the synthesis of functionalized homoallylic alcohols. Particularly, chiral alpha-substituted allylic boronate derivatives are known to give high chirality transfer in their reactions with aldehydes, thus allowing access to homoallylic alcohols in an enantioselective manner. Unfortunately, the only method currently available to access alpha-chiral allylic boronates is quite tedious and requires a chiral auxiliary. This represents a major limitation in the use of alpha-chiral allylic boronates. The new methodology presented in this communication provides a solution to this problem; it employs copper (I) as metal catalyst, a chiral phosphoramidite ligand, and a Grignard reagent as nucleophilic source for an efficient allylic substitution reaction on 3-chloro-1-propenyl boronates. This process was optimized with respect to several variables including solvent, ligand, boronate (R1) and Grignard reagent (R2). Thus far, alpha-substituted allylic boronates with enantiopurities as high as 87.0% ee and high regiocontrol were isolated using this approach.
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Asymmetric Reactions and Syntheses, Physical Organic Chemistry, Combinatorial Chemistry, Total Synthesis
8:00 PM-10:00 PM, Sunday, 26 March 2006 Georgia World Congress Center -- Ex. Hall B4, Poster
Sci-Mix
Division of Organic Chemistry |
