Mi-Sook Yoo

Trimeric Cinchona alkaloid phase-transfer catalyst: α,α′,α′′-tris[O(9)-allylcinchonidinium]mesitylene tribromide

A trimeric Cinchona alkaloid ammonium salt, α,α′,α′′-tris[O(9)-allylcinchonidinium]mesitylene tribromide has been prepared as a novel phase-transfer catalyst. The catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using the trimer catalyst showed high enantioselectivity (90–97% ee).

Highly efficient ortho-fluoro-dimeric cinchona-derived phase-transfer catalysts

A series of cinchona alkaloid-derived dimeric quaternary ammonium salts were prepared as chiral phase-transfer catalysts by the introduction of various functional groups on the phenyl ligand. Among them, the 2-F-substituted derivative 21 showed the highest enantioselectivity in the alkylation of the glycine anion equivalent 1 (97 to >99% ee).

Synthesis and application of dimeric Cinchonaalkaloid phase-transfer catalysts:α,α′-bis[O(9)-allylcinchonidinium]-o,m, or p-xylene dibromide

A dimeric Cinchona alkaloid ammonium salt, α,α′-bis[O(9)-allylcinchonidinium]-m-x ylene dibromide 4, has been developed as a new efficient phase-transfer catalyst; the catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using 4 provided 7 in a high enantiomeric excess (90–99% ee).