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A chiral ligand-mediated asymmetric addition of a lithium BHA ester enolate to an aldehyde.

Yumiko Y Nomura, Mayu M Iguchi, Hirohisa H Doi, and Kiyoshi K Tomioka

Chem Pharm Bull (Tokyo) 50(8):1131-4 (2002) PMID 12192154

The asymmetric reaction of a lithium enolate generated from a BHA (2, 6-di-tert-buty-4-methoxyphenyl) propanoate was allowed to react with benzaldehyde in the presence of a diether-type chiral ligand affording the corresponding anti-aldol product in a moderate enantioselectivity. A tetradentate ligand induced better enantioselectivity albeit relative loss of anti-selectivity. A variation of lithiating amide agent affected the selectivity, indicating involvement of an amine as a component of the mixed aggregate. Absolute configuration of some of the aldol products was determined by standard transformations.

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