Org Prep Daily

September 5, 2006

DMP

Filed under: procedures — milkshake @ 10:09 pm

newdmp.gif

Dess-Martin Periodnane (DMP)

In a wide-mouth flask with a large stirbar, a mixture of TsOH.monohydrate 0.5g and acetic anhydride 400mL was heated on oil bath to 80C. With vigorous stirring, IBX 100g was slowly added, spoon-by-spoon with internal thermometer checking the reaction mixture temperature. (It is very important to avoid overheating – the overheated mixture can produce a violent runaway and /or explosion). After complete IBX addition the mixture was stirred at 80C for 2 hours. The stirbar was removed, the mixture was placed into a cold room (+4C) overnight. The crystallized product was collected by filtration under positive pressure of nitrogen using a large (0.5L) sintered funnel. The product was washed with anhydrous ether (200mL, in portions) under positive pressure and dried by passing nitrogen through the solid.

Y = 134.2g (88.5% th) of a white powder. The product is best stored in a fridge in a tight bottle.

This procedure is from Ireland, JOC (1993), 2899

2 Comments »

  1. You will get higher quality DMP if the Ireland procedure is altered as follows:

    1) DMP crystals are quite dense. I found it easier to decant off most of the mother liquor via cannula. I then added 20-40 mL of cold acetic anhydride to wash off the remaining impurities, followed by 20-40 mL of 1:1 acetic anhydride:ether and final wash with ether. All of these steps can be performed using cannula techniques, but the final wash is best done on a sintered funnel.

    Replacing the acetic anhydride directly with ether, as recommended by the original procedure, will result in precipitation of very fine DMP that sticks to the crystals and results in a product that hydrolyzes very easily. This modification will result in slightly lower yield but the DMP product keeps much better and gives better yields (typically 97% to quantitative) in most oxidations since less of the alcohol becomes stuck in the hydrolyzed and partially polymerized DMP/IBX.

    2) I would advise dividing the product into small 10-20 g batches and opening only one bottle at a time. This will markedly reduce the amount of DMP lost in hydrolysis, especially in moist climates. DMP requires water for activation, but during storage water is highly detrimental!

    Comment by PMP — October 10, 2006 @ 4:29 pm

  2. Thank you, this is very helpful instruction! Also, one does not have to get water in it, to get DMP oxidation going – one drop of tBuOH does it. People have been also  doing DMP oxidations in presence of pyridine (to buffer the acidity with very unstable substrates) and pyridine is a good initiator as well.

    Comment by milkshake — October 10, 2006 @ 5:22 pm


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