A Powerful Chiral Phosphoric Acid Catalyst for Enantioselective Mukaiyama-Mannich Reactions.
A new BINOL-derived chiral phosphoric acid bearing 2,4,6-trimethyl-3,5-dinitrophenyl substituents at the 3,3'-positions was developed. The utility of this chiral phosphoric acid is demonstrated by a highly enantioselective (ee up to >99 %) and diastereoselective (syn/anti up to >99:1) asymmetric Mukaiyama-Mannich reaction of imines with a wide range of ketene silyl acetals. Moreover, this method was successfully applied to the construction of vicinal tertiary and quaternary stereogenic centers with excellent diastereo- and enantioselectivity. Significantly, BINOL-derived N-triflyl phosphoramide constitutes a complementary catalyst system that allows the title reaction to be applied to more challenging imines without an N-(2-hydroxyphenyl) moiety.
Molecular Catalyst Research Center, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi, 487-8501, Japan. fengtaozhou@163.com.
Fengtao
F
Zhou
Molecular Catalyst Research Center, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi, 487-8501, Japan. hyamamoto@isc.chubu.ac.jp.
Hisashi
H
Yamamoto
Brønsted acids; Mukaiyama-Mannich reactions; asymmetric catalysis; chiral phosphoric acids; quaternary stereogenic centers