Benzyltriethylammonium Permanganate


[68844-25-7]  · C13H22MnNO4  · Benzyltriethylammonium Permanganate  · (MW 311.26)

(oxidant, used for the oxidation of alkanes and arenes to alcohols or ketones,1,2 ethers to esters,3 primary alcohols to methylene diesters,4 secondary alcohols to ketones,4 amines to amides,5 aldehydes to carboxylic acids,6 and sulfides or sulfoxides to sulfones7)

Physical Data: 8 purple solid, decomposes at 101 °C (TDA), 127-129 °C (melting point tube).

Solubility: 8 4.97 × 10-3 M in H2O; 5.76 × 10-2 M in CH2Cl2; 4.6 × 10-3 M in CHCl3; insol. CCl4 and toluene.

Analysis of Reagent Purity: ε = 2530 ± 30 L mol-1 cm-1 at 526 nm8 or iodometric titration.1

Preparative Methods: 1 a solution of Benzyltriethylammonium Chloride (227.8 g, 1.00 mol) in 200 mL of water is added slowly dropwise to a solution of Potassium Permanganate (158.0 g, 1.00 mol) in 4.7 L of water. Violet crystals are recovered by filtration and dried under vacuum at rt. Yield: 294.8 g (95%).

Handling, Storage, and Precautions: oxidant, store small amounts (10-100g) in glass vessels at or below rt. Decomposes violently when heated above 50 °C or subjected to shocks.9,10 Room temperature should not be exceeded when drying under vacuum.9

Oxidation of Alkanes and Arenes.1,2

Certain alkanes and the benzylic carbon of alkyl-substituted arenes are oxidized by benzyltriethylammonium permanganate in methylene chloride or acetic acid to give alcohols or ketones. Good yields (based on unrecovered starting material) are obtained (25-98%), but the extent of conversion (based on the amount of hydrocarbon used as starting material) is quite low (11-44%). Some typical examples are shown in eqs 1-4.

Oxidation of Ethers to Esters.3

Benzyltriethylammonium permanganate oxidizes ethers to esters in good yield under nonaqueous conditions in reactions that are reminiscent of those reported for Ruthenium(VIII) Oxide. The advantage of using benzyltriethylammonium permanganate is that it does not result in the degradation of aromatic ethers. Examples reported include eqs 5-7.

Oxidation of Alcohols.4

The oxidation of secondary alcohols to ketones with this reagent is accompanied by a certain amount of carbon-carbon bond cleavage. Primary alcohols are oxidized to carboxylates, which undergo further reaction with methylene chloride when it is used as the solvent. The principle products are methylene diesters. Examples include those shown in eqs 8-10.

Oxidation of Amines.5

Tertiary amines are oxidized to N,N-dialkylamides in good yields. Primary and secondary amines are less selectively oxidized. Examples include eqs 11 and 12.

Oxidation of Aldehydes.6

Aldehydes are oxidized by benzyltriethylammonium permanganate to carboxylic acids in organic solvents at rt, e.g. eqs 13 and 14.

Oxidation of Sulfides and Sulfoxides.7

Sulfides and sulfoxides are oxidized cleanly to the corresponding sulfones by benzyltriethylammonium permanganate under nonaqueous conditions. Examples include eqs 15-18.

The reactions of benzyltriethylammonium permanganate are very similar to those of other quaternary ammonium and phosphonium permanganates such as Tetra-n-butylammonium Permanganate and Methyltriphenylphosphonium Permanganate. Similar reactions can also be carried out more simply by use of phase transfer processes which are described under Potassium Permanganate.

1. Schmidt, H-J.; Schäfer, H. J.; AG(E) 1979, 18, 68.
2. Sangaiah, R.; Krishna Rao, G. S. S 1980, 1018.
3. Schmidt, H-J.; Schäfer, H. J. AG(E) 1979, 18, 69.
4. Schmidt, H-J.; Schäfer, H. J. AG(E) 1981, 20, 109.
5. Schmidt, H-J.; Schäfer, H. J. AG(E) 1981, 20, 104.
6. Scholz, D. M 1979, 110, 1471.
7. Scholz, D. M 1981, 112, 241.
8. Karaman, H.; Barton, R. J.; Robertson, B. E.; Lee, D. G. JOC 1984, 49, 4509.
9. Jager, H.; Lütolf, J.; Meyer, M. W. AG(E) 1979, 18, 786.
10. Schmidt, H-J.; Schäfer, H. J. AG(E) 1979, 18, 787.

Donald G. Lee

The University of Regina, SK, Canada

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