ORGANIC
LETTERS
2000
Vol. 2, No. 18
2773-2776
A Highly Chemoselective Oxidation of
Alcohols to Carbonyl Products with
Iodosobenzene Diacetate Mediated by
Chromium(III)(salen) Complexes:
Synthetic and Mechanistic Aspects
,†
Waldemar Adam,†,‡ Saumen Hajra,* Markus Herderich,§ and
Chantu R. Saha-Mo1ller†
Institut fu¨r Organische Chemie and fu¨r Lebensmittel Chemie, UniVersita¨t Wu¨rzburg,
Am Hubland, D-97074 Wu¨rzburg, Germany
Received June 2, 2000
ABSTRACT
The catalytic oxidation of the allylic alcohols 1d−n with iodosobenzene diacetate, mediated by the [CrIII(salen)]X complex, affords the respective
enones in excellent chemoselectivity for Cl- as counterion [complex A(Cl)], while for the counterions TfO- [complex A(TfO)] and PF6- [complex
A(PF )] nearly equal amounts of enone and epoxide are observed. This counterion-dependent oxidation of allylic alcohols by CrIII(salen) complexes
6
is rationalized in terms of Lewis acid catalysis by the complex A(Cl) and redox catalysis for A(TfO) and A(PF ).
6
The oxidation of alcohols to carbonyl products is a pivotal
transformation in organic chemistry, which has received
much attention over the years, especially the search for
versatile and selective reagents in catalytic applications.1
Particularly in the past decade, the oxidizing properties of
hypervalent iodine compounds2 have been of increasing
interest, of which the highly utilized pentavalent iodine
reagents stand out, namely, the Dess-Martin periodinane3
and its direct precursor o-iodoxybenzoic acid.4 Despite their
utility and popularity, a serious disadvantage of such iodine-
(V) oxidants is their explosive nature, which obliges their
impromptu generation, since these potentially dangerous
reagents should not be stocked.5
In contrast, the facile, safe to use, readily available, and
persistent iodine(III) oxidants, e.g., iodosobenzene6,7 and
most notably its diacetate,5,8 have, in comparison, not been
used very much. Consequently, only few selective catalytic
oxidations with iodine(III) reagents are known, especially
† Institut fu¨r Organische Chemie.
uni-wuerzburg.de.
(5) Tohma, H.; Takizawa, S.; Maegawa, T.; Kita, Y. Angew. Chem., Int.
Ed. 2000, 39, 1306-1308.
§ Institut fu¨r Lebensmittel Chemie.
(1) Muzart, J. Chem. ReV. 1992, 92, 113-140.
(6) Adam, W.; Gelalcha, F. G.; Saha-Mo¨ller C. R.; Stegmann, V. R. J.
Org. Chem. 2000, 65, 1915-1918.
(2) (a) Stang, P. J.; Zhdankin, V. V. Chem. ReV. 1996, 96, 1123-1178.
(b) Varvoglis, A. HyperValent Iodine in Organic Synthesis; Academic
Press: London, 1997. (c) Wirth, T.; Hirt, U. H. Synthesis 1999, 1271-
1287. (d) Moriarty, R. M.; Prakash, O. Org. React. 1999, 54, 273-418.
(3) (a) Dess, D. B.; Martin, J. C. J. Am. Chem. Soc. 1991, 113, 7277-
7287. (b) Meyer, S. D.; Schreiber, S. L. J. Org. Chem. 1994, 59, 7549-
7552.
(7) Yokoo, T.; Matsumoto, K.; Oshima, K.; Utimoto, K. Chem. Lett.
1993, 571-572.
(8) (a) Mu¨ller, P.; Godoy, J. Tetrahedron Lett. 1981, 22, 2361-2364.
(b) Mico, A. D.; Margarita, R.; Parlanti, L.; Vescovi, A.; Piancatelli, G. J.
Org. Chem. 1997, 62, 6974-69777.
(9) (a) Samsel, E. G.; Srinivasan, K.; Kochi, J. K. J. Am. Chem. Soc.
1985, 107, 7606-7617. (b) Srinivasan, K.; Kochi, J. K. Inorg. Chem. 1985,
24, 4671-4679. (c) Ryan, K. M.; Bousquet, C.; Gilheany, D. G. Tetrahedron
Lett. 1999, 40, 3613-3616. (d) Khenkin, A. M.; Hill, C. L. J. Am. Chem.
Soc. 1993, 115, 8178-8186.
(4) (a) Frigerio, M.; Santagostino, M.; Sputore, S.; Palmisano, G. J. Org.
Chem. 1995, 60, 7272-7276. (b) Corey, E. J.; Palani, A. Tetrahedron Lett.
1995, 36, 3485-3488.
10.1021/ol000142y CCC: $19.00 © 2000 American Chemical Society
Published on Web 08/10/2000