Cerium(IV)-catalyzed deprotection of acetals and ketals under mildly basic conditions

Angewandte Chemie - International Edition

Volumn 38, Issue 21, 1999, Pages 3207-3209

  Markó, István E ^a   Ates, Ali ^a   Gautier, Arnaud ^a   Leroy, Bernard ^a   Plancher, Jean Marc ^a   Quesnel, Yannick ^a   Vanherck, Jean Christophe ^a  

^a UNIVERSITÉ CATHOLIQUE DE LOUVAIN   (Belgium)

Author keywords

Aldehydes; Cerium; Homogeneous catalysis; Ketones; Protecting groups

Indexed keywords

ACETAL; ALDEHYDE; CERIUM; KETONE;

ARTICLE; CATALYSIS; CHEMICAL REACTION; CHEMICAL STRUCTURE; POTENTIOMETRY; REACTION ANALYSIS;

EID: 0033517685     PISSN: 14337851     EISSN: None     Source Type: Journal    
DOI: 10.1002/(SICI)1521-3773(19991102)38:21<3207::AID-ANIE3207>3.0.CO;2-I     Document Type: Article

References (19)

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6. A. Ates, PhD Thesis, Université catholique de Louvain, in preparation.
7. The sensitivity of this aldol product 2 towards acidic conditions is further illustrated by its complete transformation into 3 during attempted purification by chromatography on silica gel.
8. A. Ates, A. Gautier, B. Leroy, J. M. Plancher, Y. Quesnel, I. E. Markó, Tetrahedron Lett. 1999, 40, 1799-1802.
9. a) T. L. Ho, "Cerium(IV) Oxidation of Organic Compounds" in Organic Synthesis by Oxidation with Metal Compounds (Eds.: W. J. Mijs, C. R. H. I. de Jonge). Plenum Press, New York, 1986;
10. b) J. R. Hwu, M. L. Jain, S. C. Tsay, G. H. Hakimelahi, Tetrahedron Lett. 1996, 37, 2035-2038, and references therein.
11. a) T. L. Ho, Synthesis 1978, 936;
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14. So far, we have not been able to find reaction conditions under which unmasking of a dioxolane group could be accomplished chemoselectively in the presence of a tert-butyldimethylsilyl (TBDMS) protecting group.
15. 3, competitive oxidation to give the 2-hydroxyethyl ester derivative takes place.
16. With 2.5 equivalents of CAN, epimerization takes place, affording a near thermodynamic mixture of axial and equatorial product (60:40).
17. Deprotection of ketal 6 with 2.5 equivalents of CAN resulted in quantitative formation of tert-butylcyclohexanone. However, no 1,2-octanediol could be isolated in this experiment. In contrast, removal of the dioxolane protecting group with 3 mol % CAN in borate buffer (pH 8) afforded not only the desired ketone (95%) but also 1,2-octanediol (97%); hence, a different mechanism operates in these two reactions.
18. Chemoselective deprotections can thus be realized by using dioxolane protecting groups with different steric demands.
19. 4, and other lanthanide salts were inert under our reaction conditions.