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Synfacts 2008(5): 0542-0542  
DOI: 10.1055/s-2008-1072550
Polymer-Supported Synthesis
© Georg Thieme Verlag Stuttgart · New York

Asymmetric Alkylation Using Polymer-Supported Cinchona Ammonium Salts

Contributor(s): Yasuhiro Uozumi, Yutaka Matsuura
Q. Shi, Y.-J. Lee, M.-J. Kim, M.-K. Park, K. Lee, H. Song, M. Cheng, B.-S. Jeong, H.-g. Park*, S.-s. Jew*
Shenyang Pharmaceutical University, P. R. of China; Seoul National University and Yeungnam University, Gyeongsan, Korea
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Publication History

Publication Date:
23 April 2008 (online)

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Significance

Polymer-supported cinchona ammonium salts were prepared and used as chiral phase-transfer catalysts (PTC). The catalysts 4a-d were prepared from the (-)-hydrocinchonidine 1 and benzyl bromide analogues 2a-d in two steps (eq. 1). The asymmetric alkylation of N-(diphenylmethylene)glycine tert-butyl ester 5 with benzyl bromide took place in the presence of 20 mol% of catalysts 4a-d and 50% KOH in toluene-chloroform to give 6 in 81-88% yield (eq. 2). Among the catalysts, 4d showed the highest enantioselectivity (95% ee).