Enantioselective alkylation of lactams and lactones can be realized up to 98% ee by deprotonation with a chiral tetradentate lithium amide (4b) in the presence of lithium bromide, and subsequent alkylation with active alkylating agents in non-chelating solvents.
Enantioselective alkylation at the ?-position of cyclic ketones using a chiral lithium amide as a base in the presence of lithium bromide
โ Scribed by Murakata, Masatoshi; Nakajima, Makoto; Koga, Kenji
- Book ID
- 120929725
- Publisher
- The Royal Society of Chemistry
- Year
- 1990
- Tongue
- English
- Weight
- 237 KB
- Volume
- 0
- Category
- Article
- ISSN
- 0022-4936
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๐ SIMILAR VOLUMES
An efficient enantioselective alkylation of the lithium enolates of cyclohexanone and ltetralone with reactive alkyl halides was realized using a stoichiometric amount of a tetradentate chiral amine as a ligand for the lithium in the presence of lithium bromide in toluene.
Ihe prochiral lithium 2,2,6-trimethylcyclohexenolate (2) was prepared from ketone 1 by deprotonation with lithium (S,S)-a,a'-dimethyldibenzylamide(4). Reaction of 2 with carbon dioxide at low temperature followed by methylation with metFy1 iodide yielded the corresponding ester 3 with an e.e. of 67%
Lithium N-trityl-N-(R)-1-phenylethylamide (6) is a readily available and useful reagent for the enantioselective (20:1) conversion of 4-t-butylcyclohexanone to the corresponding (S)-enolate. This reaction provides access to numerous useful chiral compounds.