Rhodium
(Chief Bee)
07-04-02 20:20
No 328762
      Butanediol or THF to GBL using KMnO4/CuSO4
(Rated as: good read)
    

Solvent-free Permanganate Oxidations
Tet Lett 42(34), 5833-5836 (2001) (../rhodium/pdf /solventfree.kmno4.oxidation.pdf)

The oxidant is prepared by grinding equal amounts of potassium permanganate and copper sulfate pentahydrate in a mortar until homogeneous, or preferably by adding a concentrated aqueous solution of potassium permanganate to alumina, giving a paste which is then ground with an equal amount of copper sulfate pentahydrate. The substrate (2 mmol) is added to a portion of the oxidant (~4 g) in a 25 mL round bottomed flask and stirred magnetically until TLC analysis indicates a completed reaction. The residue is then washed with a minimum amount of solvent (methylene chloride, hexane and/or ether). Evaporation of the solvent gives a product that is of acceptable purity for most purposes. If greater purity is required, the product can be distilled.

Tetrahydrofuran -> GBL (6h, 70% yield)
1,4-Butanediol -> GBL (14h, 95% yield)


Entropy just isn't what it used to be.
 
 
 
 
    Rhodium
(Chief Bee)
09-29-04 15:21
No 533747
      THF --Mn2O7--> GBL (86%)
(Rated as: good read)
    

[Selective oxidation of organic compounds with Mn(VII) Oxide]
Martin Trmel & Manuel Russ
Angewandte Chemie 99(10), 1037-1038 (1987) (../rhodium/pdf /thf2gbl.mn2o7.pdf)

2 KMnO4 + 2 H2SO4 -> Mn2O7 + 2 KHSO4 + H2O

3 THF + 2 Mn2O7 -> 3 GBL + 4 MnO2 + 3 H2O


Mn(VII) Oxide
To a stirred and cooled mixture of 24 mL H2SO4 and 100 mL anhydrous CCl4, 16.3g finely ground KMnO4 is added while keeping the temperature between 20-25C. After stirring the solution for several hours, and the deep red red solution is decanted from the formed sediment and stored at 4C.  It is possible to prepare batches up to three times this size.

Titration
To 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 Mn2O7.

Oxidation
The [THF] is dissolved in an 1:1 mixture of acetone/CCl4 (MeOAc & EtOAc also works), and after cooling to -45C the Mn2O7 is  added with stirring (0.7 molar equivalents as a 2.5% solution in CCl4) at such a rate that the temperature does not increase above -40C.  After the addition, the solution is stirred for 5 min at -45C and excess Mn2O7 is destroyed by the dropwise addition of IPA. The solution is allowed to warm to room temperature, the precipitated MnO2 is filtered off and the solvent evaporated. The product is then isolated by vacuum distillation. Yield of GBL 86%.

The Hive - Clandestine Chemists Without Borders