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Synfacts 2015; 11(1): 0109
DOI: 10.1055/s-0034-1379724
Polymer-Supported Synthesis
© Georg Thieme Verlag Stuttgart · New York

Asymmetric α-Benzylation with Cinchonidium Salt Based Polymers

Contributor(s):
Yasuhiro Uozumi
,
Makoto Nagaosa
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
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Further Information

Publication History

Publication Date:
15 December 2014 (online)

 
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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).


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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.


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