Onium Phenoxides and Related Compounds

Onium Phenoxides and Related Compounds as Bronsted Base Catalysts 

As described in this chapter, numerous recent efforts to elaborate chiral onium salts have greatly expanded their use as asymmetric catalysts in organic synthesis. However, the full potential of chiral onium salts is yet to be realized in terms of general applicability. Continuous efforts should be made toward the design and development of conceptually new catalysts, and to understanding the relationship between catalyst structure and stereocontrolling ability. 

3 (a) Dehmlow, E.V. and Dehmlow, S.S. (1993) Phase Transfer Catalysis, 3rd edn, Wiley-VCH Verlag GmbH, Weinheim  

Verlag Chemie, New York, pp. 727-756 (b) Shioiri, T. (1997) Handbook of Phase-Transfer Catalysis (eds Y. Sasson and R. Neumann), Blackie Academic Professional, London, ch. 14, pp. 

Process Res. Dev., 12, 679 (o) Mamoka, K. (ed.) (2008) Asymmetric Phase Transfer Catalpis, Wiley-VCH Verlag GmbH, Weinheim (p) Jew, S.-S. and Park, H.-G. (2009) Chem. Commun., 7090  

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In contrast to the neutral property of onium bromides, onium phenoxides and carboxylates work as base catalysts by considering the general basicity of the phe-noxide and carboxylate anions (Figure 14.4). Based on this property, chiral onium phenoxides and related compounds have been employed both as Lewis and Bron-sted base catalysts for homogeneous reachons [6]. 

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