[Selective oxidation of organic compounds with Mn(VII) Oxide]Martin Trömel & Manuel RussAngewandte Chemie 99(10), 1037-1038 (1987)
(
https://www.thevespiary.org/rhodium/Rhodium/pdf/thf2gbl.mn2o7.pdf)
2 KMnO
4 + 2 H
2SO
4 -> Mn
2O
7 + 2 KHSO
4 + H
2O
3 THF + 2 Mn
2O
7 -> 3 GBL + 4 MnO
2 + 3 H
2O
Mn(VII) OxideTo a stirred and cooled mixture of 24 mL H
2SO
4 and 100 mL anhydrous CCl
4, 16.3g finely ground KMnO
4 is added while keeping the temperature between 20-25°C. After stirring the solution for several hours, and the deep red red solution is decanted from the formed sediment and stored at 4°C. It is possible to prepare batches up to three times this size.
TitrationTo determine the exact concentration, 0.3 mL of the above solution is mixed with 30 mL water and with stirring, 1.5g KI and 4 mL glacial acetic acid is added thereto. The resulting solution is then titrated with 0.100 M thiosulfate, each mL corresponding to 2.2 mg Mn
2O
7.
OxidationThe [THF] is dissolved in an 1:1 mixture of acetone/CCl
4 (MeOAc & EtOAc also works), and after cooling to -45°C the Mn
2O
7 is added with stirring (0.7 molar equivalents as a 2.5% solution in CCl
4) at such a rate that the temperature does not increase above -40°C. After the addition, the solution is stirred for 5 min at -45°C and excess Mn
2O
7 is destroyed by the dropwise addition of IPA. The solution is allowed to warm to room temperature, the precipitated MnO
2 is filtered off and the solvent evaporated. The product is then isolated by vacuum distillation. Yield of GBL 86%.