CrIII(salen) impregnated on silica for asymmetric ring opening reactions and its recovery via desorption/re-impregnation

Tetrahedron Letters

Volumn 44, Issue 49, 2003, Pages 8815-8817

  Dioos, Bart M L ^a   Jacobs, Pierre A ^a  

^a UNIVERSITY OF LEUVEN   (Belgium)

Author keywords

[No Author keywords available]

Indexed keywords

CHROMIUM; SILICON DIOXIDE;

ARTICLE; BIOTRANSFORMATION; CATALYSIS; CATALYST; DESORPTION; EXTRACTION; LEACHING; RING OPENING; SOLID;

EID: 0242298256     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2003.09.203     Document Type: Article

References (17)

1. Martinez L.E., Leighton J.L., Carsten D.H., Jacobsen E.N. J. Am. Chem. Soc. 117:1995;5897-5898.
2. Larrow J.F., Schaus S.E., Jacobsen E.N. J. Am. Chem. Soc. 118:1996;7420-7421.
3. Baleizao C., Gigante B., Sabater M.J., Garcia H., Corma A. Appl. Catal. A: Gen. 228:2002;279-288.
4. Angelino M.D., Laibinis P.E. J. Polym. Sci.: Part A: Polym. Chem. 37:1999;3888-3898.
5. Hansen K.B., Leighton J.L., Jacobsen E.N. J. Am. Chem. Soc. 118:1996;10924-10925.
6. Gigante B., Corma A., Garcia H., Sabater M.J. Catal. Lett. 68:2000;113-119.
7. Kim G.J., Park D.W. Catal. Today. 63:2000;537-547.
8. Annis D.A., Jacobsen E.N. J. Am. Chem. Soc. 121:1999;4147-4154.
9. Peukert S., Jacobsen E.N. Org. Lett. 8:1999;1245-1248.
10. Silica gel 60 for preparative column chromatography was bought from Fluka.
11. A catalyst/silica ratio of 1.25 wt%, corresponding to 20 μmol/gram, showed optimal performance. Based on a screening experiment in which a range of catalyst loadings were tested, this sample combined low leaching degrees with good enantioselectivity. Higher catalyst/silica ratios of 2.5, 5.0 and 10 wt% suffered from leaching varying between 5 and 30%.
12. Hansen K.B., Leighton J.L., Jacobsen E.N. J. Org. Chem. Soc. 118:1996;10924-10925.
13. All enantiomeric/diastereomeric excesses were determined by chiral GC on a Chrompack-CHIRASIL-DEX CB column (0.32 mm×0.25 μm×25 m) using FID detection.
14. Dioos B.M.L., Jacobs P.A. Tetrahedron Lett. 44:2003;4715-4717.
15. 3+ ions have two absorption bands at about 430 and 614 nm due to d-d transitions.
16. In an homogeneous reference experiment with 375 ppm of Cr(salen) carried out in hexane, the conversion and e.e. after 24 h was 25 and 26%, respectively. Consequently, under the conditions described in Table 1, the amount of complex corresponding to a degree of leaching of 1% should not contribute significantly to the conversion.
17. During solvent evaporation the catalyst precipitates, while both epoxide and ring opened products can be extracted in hexane, in which the catalyst-precipitate will not dissolve.