Abstract
The enantioselective aldol reactions of ketone lithium enolates with aldehydes mediated chiral lithium amides were extensively investigated. The chiral amino ethers 4a– 4l and diamines 16a, b were prepared from α-amino acids. The reaction conditions and the substituent effects of chiral lithium amides were examined using 4a– 4l and 16a, b in the aldol reaction of lithium enolate of 2,2-dimethyl-3-pentanone ( 17a) with benzaldehyde. When the lithium amide from 4b or 4c was used, 18a was obtained in 92–93% yield and 68% enantiomeric excess. Reactions of various ketones 17a– 17d with aldehydes afforded the β-hydroxy-α-methyl carbonyl compounds 18a– 18k in 40–95% yield and 10–77% enantiomeric excess. The best result of 77% enantiomeric excess was realized in the aldol reaction of 17a with 1-naphthaldehyde using the chiral lithium amide from 4b. The aldols 18i– 18k were easily converted to the carboxylic acid derivatives 19a– 19c of 40–60% enantiomeric excess.
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