Design of Brønsted acid-assisted chiral Brønsted acid catalyst bearing a bis(triflyl)methyl group for a Mannich-type reaction.
[Structure: see text] A new Brønsted acid-assisted chiral Brønsted (chiral BBA) acid catalyst (1) was developed by substituting a hydroxy group of optically active 1,1'-bi(2-naphthol) with a stronger Brønsted acidic group such as a bis(trifluoromethanesulfonyl)methyl group. The enantioselective Mannich-type reaction of ketene silyl acetals with aldimines catalyzed by (R)-1 in the presence of stoichiometric achiral proton sources gave (S)-beta-amino esters in high yield with moderate to good enantiomeric excesses.
Hasegawa
Aiko
A
Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan.
Naganawa
Yuki
Y
Fushimi
Makoto
M
Ishihara
Kazuaki
K
Yamamoto
Hisashi
H