期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 14, 期 7, 页码 2052-2059出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.200701439
关键词
asymmetric catalysis; circular dichroism; combinatorial chemistry; high-throughput screening; solid-phase synthesis
A library of imidazoline-aminophenol ligands was synthesized on solid supports. After immobilization of chiral chloromethylimidazolines 1 and 2 onto the polystyrylsulfonyl chloride, nucleophilic substitution with (R)or (S)-phenylethylamine (3 and 4) provided four combinations of polymer-supported imidazoline-amine ligands. Further reductive alkylation using salicylaldehydes 7-10 provided a series of imidazoline-aminophenol ligands (L9-L24). Analysis by solid-phase catalysis/circular dichroism high-throughput screening of a copper-catalyzed Henry reaction revealed that ligand L25, comprising a (S,S)-diphenylethylenediamine-derived imidazoline, (S)-phenyle-thylamine, and dibromophenol, was highly efficient, thus providing the adduct of nitromethane and benzaldehyde in 95% ee. The combination of stereogenic centers was crucial in promoting the highly stereoselective reactions. The unique reaction sphere of L25 was also examined in a FriedelCrafts alkylation of indole and nitroalkene to give the adduct in up to 83% ee.
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