Imidazolium Dichromate

[109201-26-5]  · C6H10Cr2N4O7  · Imidazolium Dichromate  · (MW 354.20)

(mild selective reagent for the oxidation of allylic and benzylic alcohols to the corresponding carbonyl compounds)

Alternate Name: IDC.

Physical Data: mp 130-131 °C; nonhygroscopic; air stable yellow crystals.

Solubility: readily sol DMF, DMSO; very slightly sol acetone, dichloromethane, trichloromethane.

Preparative Method: easily prepared by the addition of Imidazole to a solution of an equimolar amount of Chromium(VI) Oxide in a minimum amount of water.1 The yellow crystals are collected, washed with acetone, and dried in vacuo at rt.

Handling, Storage, and Precautions: all chromium(VI) reagents must be handled with care. The mutagenicity of chromium(VI) compounds is well documented.2 This reagent should be handled in a fume hood.

Oxidation of Allylic and Benzylic Alcohols to Carbonyl Compounds.

Imidazolium dichromate oxidizes cinnamyl alcohol and benzhydrol to cinnamaldehyde (91%) and benzophenone (93%), respectively, at rt.1 Allylic alcohols are oxidized faster than benzylic alcohols and saturated aliphatic alcohols react slowest. Geraniol is oxidized to geranial (82% yield) with 6% (E) to (Z) isomerization at the double bond. 4-(3-Hydroxypropyl)benzyl alcohol is selectively oxidized to 4-(3-hydroxypropyl)benzaldehyde (eq 1). The selectivity achieved with IDC is comparable to that of 4-(Dimethylamino)pyridinium Chlorochromate (DMAP.HCrO3Cl).3,4

1. Kim, S.; Lhim, D. C. BCJ 1986, 59, 3297.
2. Cupo, D. Y.; Wetterhahn, K. E. Cancer Res. 1985, 45, 1146.
3. Guziec, F. S., Jr.; Luzzio, F. A. JOC 1982, 47, 1787.
4. Guziec, F. S., Jr.; Luzzio, F. A. OPP 1988, 20, 533.

Fillmore Freeman

University of California, Irvine, CA, USA

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