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DOI: 10.1055/s-2004-822365
Catalytic Enhancement Effect of a Chiral Ligand on the Asymmetric Mannich-Type Reactions of Menthyl Alkanoates with Aldimines
Publication History
Received
15 April 2004
Publication Date:
10 May 2004 (online)


Abstract
The lithium enolate of menthyl acetate underwent the Mannich-type reaction with benzaldehyde PMP-imine in toluene to give the corresponding adduct with 70:30 dr. The diastereoselectivity was dramatically improved to 97:3 dr by the addition of chiral 1,2-diphenyl-1,2-dimethoxyethane. The reaction of menthyl isobutyrate with imines was also influenced by a catalytic amount (5 mol%) of a chiral tridentate aminodiether ligand to give the corresponding β-lactams in high enantioselectivities. Matching and mismatching phenomena were observed by the reaction of l- and d-menthyl isobutyrates.
Key words
addition reactions - asymmetric synthesis - asymmetric catalysis - imines - lithium