Methyltriphenylphosphonium Permanganate

Ph3+PMe MnO4-

[73335-41-8]  · C19H18MnO4P  · Methyltriphenylphosphonium Permanganate  · (MW 396.28)

(oxidant, useful for the conversion of alkenes into cis-diols1)

Physical Data: purple solid; decomposes at 102 °C.2

Solubility: 1.17 × 10-3 M in H2O; 1.15 M in CH2Cl2; 0.941 M in CHCl3; insol toluene, carbon tetrachloride.2

Analysis of Reagent Purity: ε = 2530 ± 30 L mol-1 cm-1 at 526 nm.2 IR (KBr) 3420, 3050, 2980, 2890, 1585, 1485, 1435, 1120, 905, 750, 725, and 695 cm-1;3 1H NMR (CD2Cl2) d 7.80 and 2.80 ppm.2

Preparative Method: Potassium Permanganate (3.07 g, dissolved in a minimum of H2O) is added dropwise to Methyltriphenylphosphonium Bromide (4.63 g in 100 mL of H2O) with stirring. The purple precipitate is collected, washed with water, dried over P2O5, and recrystallized from a solution of CH2Cl2 and toluene (2:1, v/v). The yield is 70-75%.3

Handling, Storage, and Precautions: oxidant; small quantities may be stored in glass vessels at or below rt. Similar compounds have been known to undergo violent thermal decompositions.4 Always work behind a protective shield.

cis-Dihydroxylation of Alkenes.

Methyltriphenylphosphonium permanganate has been used to dihydroxylate alkenes using CH2Cl2 as the solvent.1 The reaction is easy to carry out and good yields are observed. Several examples are shown in eqs 1-3.

The reactions of methyltriphenylphosphonium permanganate are very similar to those of quaternary ammonium permanganates such as Tetra-n-butylammonium Permanganate and Benzyltriethylammonium Permanganate. Similar reactions may also be carried out more simply by use of phase transfer processes that are described under Potassium Permanganate.

1. Reischl, W.; Zbiral, E. T 1979, 35, 1109.
2. Karaman, H.; Barton, R. J.; Robertson, B. E.; Lee, D. G. JOC 1984, 49, 4509.
3. Karaman, H. Ph.D. Thesis, University of Regina, 1982.
4. (a) Morris, J. A.; Mills, D. C. CI(L) 1978, 446. (b) Jager, J.; Lütolf, J.; Meyer, M. W. AG(E) 1979, 18, 786. (c) Schmidt, H.-J.; Schäfer, H. J. AG(E) 1979, 18, 787.

Donald G. Lee

University of Regina, Saskatchewan, Canada

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