PAPER: Formation and Structure of Conjugated Salen‐Cross‐Linked Polymers and Their Application in Asymmetric Heterogeneous Catalysis

Nielsen, M. M.; Thomsen, A. H.; Jensen, T. R.; Jakobsen, H. J.; Skibsted, J.; Gothelf, K. V.

Eur. J. Org. Chem. 2005, 342–347, doi: 10.1002/ejoc.200400451

Abstract

A new type of cross-linked condensation polymer was obtained by the reaction of 1,3,5-tris[(5-tert-butyl-3-formyl-4-hydroxyphenyl)ethynyl]benzene (1) with ethylenediamine. Solid-state 13C{1H} CP/MAS NMR analysis showed that the polymer was pure and highly cross-linked and powder synchrotron X-ray diffraction indicated some degree of local structural order in the polymer. A chiral manganese−salen-bridged polymer was obtained by the condensation of 1 with (1R,2R)-1,2-diphenyl-1,2-diaminoethane (3a) or (1R,2R)-1,2-diaminocyclohexane (3b) in the presence of Mn(OAc)2. These rigid chiral metal−salen polymers can catalyze the epoxidation of cis-2-methylstyrene with high conversion, diastereoselectivity and enantioselectivities of up to 67% ee. The polymeric catalyst can be reused several times without reduced activity or selectivity.

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