[AlphaScent]

Starting a new thread related to my thread about mono protection of diols.

After the mono protection, which I think has worked under my conditions, I have to oxidize the alcohol to an aldehyde.  Swern may work and not pluck off my THP and PCC is too acidic to work.  So I was thinking about some time ago I did a buffered PCC oxidation.  Using sodium acetate as a buffer for my PCC oxidation.  MY issue is that it has been a while, and dont remember the exact details.

Can anyone post a paper about buffered PCC or oxidations with THP ethers present? 

Thank you, stay cool!!  105 heat index here, holy frijoles.

[discodermolide]

One of the best reactions for this is to use bleach KBr and TEMPO in a two phase system, water / methylene chloride, rapidly stirred at between 5-10°C

[AlphaScent]

That seems great, I forgot it was a oxidation catalyst.  Just always put it in with radical polymerization.  I am going to look into that.  The issue for me is my company is cheap and may not spring for the catalyst when buffered PCC will work.

Great idea though, would love to do that reaction, sounds like fun!!

Thanks Disco.

[AlphaScent]

http://www.sigmaaldrich.com/catalog/product/aldrich/214000?lang=en&region=US

Not as bad as I though it was going to be.  Is TEMPO used in catalytic amounts??

[discodermolide]

Yes TEMPO is catalytic.
This is a very cheap reaction.

[opsomath]

I was actually thinking of this TEMPO oxidation as well, but I couldn't remember a good reference for it. Good stuff.

[AlphaScent]

Disco,

Do you have a reference paper for this reaction that I could look at for a procedure? 

Cheers

Thank you very much!!!

[discodermolide]

Here is a procedure that I used:
A solution of alcohol (9) (29 kg, 137.85 mol)
in dichloromethane (470 kg) was cooled to 0 °C.
TEMPO (210 g, 1.34 mol) was added followed by a 2.75 M
aqueous solution of potassium bromide (34.9 kg) and a 1.6
M aqueous solution of potassium hydrogen carbonate (152
kg). To the rapidly stirred two-phase mixture was added a
solution of bleach (126 kg of a 11% solution, 185.5 mol)
over 90 min. The resulting mixture was stirred for a further
40 min at 0 to 5 °C. A 1.0 M aqueous solution of sodium
thiosulphate (79.9 kg) was added. The mixture was then
warmed to room temperature within 15 min, and the layers
were separated. The organic layer was washed with water
(2 × 184 kg). Sodium sulphate (7.5 kg) was added, and the
suspension was stirred for 10 min at room temperature and
filtered. The solid was rinsed with dichloromethane (2 × 22
kg), and the combined filtrate was concentrated under
vacuum at 20-25 °C to afford aldehyde 10 (28.6 kg) as an
oil, which was used immediately in the next step:

Taken from Organic Process research & Deveopment, 2003 vol. 8 (1) pp. 92-100

You might need to scale down a bit

[AlphaScent]

Disco,

Thank you very much.  That is very awesome.  What else is awesome it that I though my 1 Kg reactions were large.  You just blew me out of the water.  I am going to keep this as a reference for sure.

I am discussed it with my boss and he thinks (as do I) that buffered PCC will work here.  I used 1:1 of potassium acetate to PCC.  Both are 1.2 eq to the alcohol, in 25 mL of DCM.  Doing a trial first.  I will let you all know.

Thank you again for your insight.  Always nice bouncing ideas of other chemists.

Cheers!!

[PhDoc]

TEMPO is a really good reagent that's practically dirt cheap. If need be, you may want to consider turning to hypervalent iodine species such as Dess-Martin period inane. It's far from cheap, however it works well under buffered conditions (i.e. 10 equivalents of NaHCO3).