Benzyltriethylammonium Chlorochromate1

[PhCH2NEt3]+[CrO3Cl]-

[106542-73-8]  · C13H22ClCrNO3  · Benzyltriethylammonium Chlorochromate  · (MW 327.77)

(a mild and neutral oxidizing agent for benzylic and allylic alcohols1)

Physical Data: mp 89 °C.

Solubility: fairly sol common organic solvents.

Form Supplied in: orange crystalline solid; not commercially available.

Preparative Method: Chromic Acid (10 g, 0.1 mol) in 3 M HCl (200 mL) is added to an aqueous solution (250 mL) of Benzyltriethylammonium Chloride (22.7 g, 0.1 mol). The crude product precipitates and can be recrystallized from acetone-water; yield 86%. The reagent prepared according to this procedure was initially described as bis(benzyltriethylammonium dichromate).2 Later, it was demonstrated that the compound obtained under these conditions is actually benzyltriethylammonium chlorochromate.3

Handling, Storage, and Precautions: the reagent is a stable orange crystalline solid. No data have been reported about storage and precautions. Chromium(VI) derivatives are reported to be toxic agents. The reagent should be handled in a fume hood.

Oxidation of Benzylic and Allylic Alcohols.

Benzyltriethylammonium chlorochromate can selectively oxidize benzylic and allylic alcohols to the corresponding carbonyl compounds in almost quantitative yield. Yields are low (30%) for primary alkanols and cycloalkanols. The reaction can be performed in HMPA at 60-80 °C for 4-6 h.2 Alternatively, the oxidation can be carried out under phase-transfer conditions.3a Yields range from 75-99%.

The reagent can be utilized for the selective oxidation of thiols to disulfides in high yield and this method has been applied to alkanethiols, arylalkanethiols, and arenethiols.2


1. Ley, S. V.; Madin, A. COS 1991, 7, 283.
2. Huang, X.; Chan, C.-C. S 1982, 1091.
3. (a) Rao, C. S.; Deshmukh, A. A.; Thakor, M. R.; Srinivasan, P. S. IJC(B) 1986, 25, 324. (b) Luzzio, F. A.; Guziec, F. S. OPP 1988, 20, 533.

Giovanni Piancatelli

University of Rome La Sapienza, Italy



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