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Recyclable Heterogeneous and Low‐Loading Homogeneous Chiral Imidazolidinone Catalysts for α‐Alkylation of Aldehydes
Author(s) -
Salvo Anna Maria Pia,
Giacalone Francesco,
Noto Renato,
Gruttadauria Michelangelo
Publication year - 2014
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201400030
Subject(s) - alkylation , catalysis , tetrafluoroborate , homogeneous , polystyrene , chemistry , ionic liquid , hexanal , organic chemistry , homogeneous catalysis , combinatorial chemistry , polymer chemistry , polymer , physics , thermodynamics
Two polystyrene‐supported and six homogeneous MacMillan imidazolidinone catalysts were prepared and tested for the asymmetric α‐alkylation of propanal with benzodithiolylium tetrafluoroborate. The chiral imidazolidinone was linked to polystyrene through the N‐3 atom or through the phenyl ring and their catalytic activity was compared with that of their unsupported precursors. This comparison has allowed us to find an unsupported catalyst that displays high catalytic activity down to 5 or 2 mol % at room temperature with a high level of enantioselectivity also when used with hexanal and 3‐phenylpropanal. In addition, one of the heterogeneous materials was revealed to be highly recyclable for at least eight cycles with no loss in efficiency working at the same levels of activity and enantioselectivity as the unsupported counterpart.