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.
addition reactions - asymmetric synthesis - asymmetric catalysis - imines - lithium