Islam MdR, Ahamed P, Haraguchi N, Itsuno S * Toyohashi University of Technology, Japan
Synthesis of Chiral Polymers Containing Thioetherified Cinchonidinium Repeating Units
and Their Application to Asymmetric Catalysis.
Tetrahedron: Asymmetry 2014;
25: 1309-1315
Key words
cinchonidium salts - chiral polymers - asymmetric α-benzylation
Significance
Chiral polymers 3 and 5 were prepared from cinchonidine dimers 1 (eqs. 1 and 2). All polymers showed high catalytic performance in the asymmetric
α-benzylation of N-diphenylmethylene glycine tert-butyl ester with benzyl bromide (eq. 3, 77–95% yield, 81–92% ee).
Comment
The polymer catalysts were recovered by filtration and reused without loss of catalytic
performance. The reaction also took place at –40 °C to give the product with improved
ee (with 3bc: 24 h, 83% yield, 95% ee). The catalytic activity and the stereoselectivity observed
with the polymeric catalysts 3 and 5 were comparable to those obtained with the homogeneous catalysts 1.
