Enantioselective 1,3-Dipolar Cycloadditions of Unsaturated Aldehydes Promoted by A Poly(ethylene glycol)-Supported Organic Catalyst

European Journal of Organic Chemistry

Volumn , Issue 3, 2004, Pages 567-573

  Puglisi, Alessandra ^a   Benaglia, Maurizio ^a   Cinquini, Mauro ^a   Cozzi, Franco ^a   Celentano, Giuseppe ^a  

^a UNIVERSITY OF MILAN   (Italy)

Author keywords

Catalyst immobilization; Chiral organic catalysts; Cycloadditions; Polymers

Indexed keywords

1,4 IMIDAZOLIDIN 4 ONE; ALDEHYDE; ETHER DERIVATIVE; IMIDAZOLE DERIVATIVE; KETONE; MACROGOL; NITRONE DERIVATIVE; ORGANIC COMPOUND; POLYMER; TYROSINE; UNCLASSIFIED DRUG;

ARTICLE; CATALYST; CATALYST IMMOBILIZATION; CATALYST SUPPORT; CHIRALITY; CYCLOADDITION; ENANTIOMER; ENANTIOSELECTIVITY; IMMOBILIZATION; MACMILLAN CATALYST; MOLECULAR STABILITY; RECYCLING; SOLUBILITY;

EID: 1242286035     PISSN: 1434193X     EISSN: None     Source Type: Journal    
DOI: 10.1002/ejoc.200300571     Document Type: Article

References (33)

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30. The absolute configuration of 6 and the other 1,3-dipolar cycloaddition products 7-9 was established by comparison of the sign of optical rotation with the value reported for the same compounds of known configuration (see ref.[8c]). The absolute configuration of the previously unreported adduct 10 was assigned on the assumption that the reaction leading to 10 followed the same stereochemical course as those leading to 6-9.
31. 3H resulted, in our hands, in yields and ee lower than those reported by MacMillan (see ref. [8c]). For instance, when 1a/HCl was employed as the catalyst, compound 7 was obtained in 64% yield and 89% ee, in contrast to the reported 70% yield and 95% ee.
32. In additional control experiments, we found that N-benzyl-C-phenylnitrone did not degrade 1a/HCl, and that the degradation of 5/HX upon recovery was independent of the catalyst's water content (from 3 to 49 equiv. of water/equivalent of catalyst; determined by Karl-Fischer titrations).
33. The recycling of 1a/HCl involved evaporation of the reaction mixture and addition of diethyl ether to the residue. The solvent was decanted and the residue was washed at least five times with diethyl ether to completely remove the reaction products. The combined ethereal phases were worked-up to isolate the product, and the catalyst was dried under vacuum to afford a waxy solid that was analyzed for degradation, by NMR spectroscopy, and then recycled.