Premium
Enantioselective 1,3‐Dipolar Cycloadditions of Unsaturated Aldehydes Promoted by A Poly(ethylene glycol)‐Supported Organic Catalyst
Author(s) -
Puglisi Alessandra,
Benaglia Maurizio,
Cinquini Mauro,
Cozzi Franco,
Celentano Giuseppe
Publication year - 2004
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.200300571
Subject(s) - chemistry , catalysis , ethylene glycol , enantioselective synthesis , organic chemistry , enantiomer , solubility , ethylene , polymer chemistry
We have developed a polymer‐supported version of MacMillan’s catalyst by anchoring a tyrosine‐derived imidazolidin‐4‐one by means of a spacer to the monomethyl ether of poly(ethylene glycol) ( M W = 5000 Da). The supported organic catalyst was employed in some 1,3‐dipolar cycloadditions involving α,β‐unsaturated aldehydes and nitrones. The products were obtained in enantiomeric excesses very similar to those observed with the non‐supported catalyst, but the chemical yields were somewhat lower. Exploiting the solubility profile of the polymeric support, the catalyst was readily separated from the reaction products, recovered, and recycled. Catalyst recycling was accompanied by a very marginal erosion (if any) of the enantioselectivity and a more‐substantial decrease in chemical efficiency. We ascribe the latter phenomenon mainly to the intrinsic instability of the catalyst under the reaction conditions, which is, however, a common feature of both the non‐supported and supported catalysts. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)