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Polystyrene‐Supported Diarylprolinol Ethers as Highly Efficient Organocatalysts for Michael‐Type Reactions
Author(s) -
Alza Esther,
Sayalero Sonia,
Kasaplar Pinar,
Almaşi Diana,
Pericàs Miquel A.
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201101730
Subject(s) - chemistry , catalysis , polystyrene , michael reaction , organic chemistry , combinatorial chemistry , trimethylsilyl azide , organocatalysis , enamine , polymer chemistry , polymer , enantioselective synthesis
α,α‐Diphenylprolinol methyl‐ and trimethylsilyl ethers anchored onto a polystyrene resin have been prepared by a copper‐catalyzed azide–alkyne cycloadditions (CuAAC). The catalytic activity and enantioselectivity displayed by the O ‐trimethylsilyl derivative are comparable to those exhibited by the best known homogeneous catalysts for the addition of aldehydes to nitroolefins and of malonates or nitromethane to α,β‐unsaturated aldehydes. The combination of the catalytic unit, the triazole linker, and the polymeric matrix provides unprecedented substrate selectivity, in favor of linear, short‐chain aldehydes, when the organocatalyzed reaction proceeds by an enamine mechanism. High versatility is noted in reactions that proceed via an iminium ion intermediate. The catalytic behavior of polystyrene‐supported α,α‐diphenylprolinol methyl ether was also evaluated in asymmetric Michael addition reactions. As a general trend, the CuAAC immobilization of diarylprolinol ethers onto insoluble polystyrene resins offers important operational advantages, such as high catalytic activity, easy recovery from the reaction mixture by simple filtration, and the possibility of extended reuse.