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Synthesis of Zirconium Phosphonate Supported L ‐Proline as an Effective Organocatalyst for Direct Asymmetric Aldol Addition
Author(s) -
Angeloni Marco,
Piermatti Oriana,
Pizzo Ferdinando,
Vaccaro Luigi
Publication year - 2014
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201301673
Subject(s) - chemistry , aldol reaction , cyclohexanone , proline , catalysis , zirconium , phosphonate , enantiomer , organocatalysis , enantioselective synthesis , organic chemistry , amino acid , biochemistry
Stable L ‐proline‐functionalized zirconium methyl‐ and/or phenylphosphonates have been prepared as amorphous solids by the precipitation of (4 R )‐4‐[(4′‐phosphonobenzyl)oxy]‐ L ‐proline and methyl‐ and/or phenylphosphonic acid with ZrOCl 2 . The supported L ‐proline catalysts were tested in the direct asymmetric aldol addition between several ketones and p ‐substituted benzaldehydes. High yields, diastereoselectivities ( anti / syn up to 92:8) and enantiomeric excesses (up to 99 % ee ) have been achieved. Moreover, an easy protocol for the efficient recovery of the catalytic system by simple centrifugation has been defined, and the effective reuse of the catalyst has been reported in the representative aldol addition of cyclohexanone with p ‐nitrobenzaldehyde. This study has shown that these L ‐proline immobilized catalytic systems can be used at least six times without loss of activity and with reproducible anti / syn and ee values.