Upvote

VOTE

Downvote

+ Organic

Posted by

Ken Heart

Fmoc protection of an amine

David Follow

I don't understand your last response. There are two amines in our discussion. TEA won't react, it's tertiary...

Upvote

VOTE

Downvote

Bergen Furniture And Design Follow

I never had succes with carbonates during acylation reactions. Try triethylamine instead

Upvote

VOTE

Downvote

Michael Roberts Follow

Piperidine and TEA are quite different. Cyclic secondary amines are rather strong nucleophiles and bases. Also, you use 1.1 equivalents TEA, not the huge over equivalency of the piperidine deprotection.

Upvote

VOTE

Downvote

David Farmer Follow

Quote from:

Did you dry the potassium carbonate? If it was just sitting around in an opened bottle it probably has significant water content.

A solid bake in a vacuum overnight at 150°C+ should do the trick. Store it in a desiccator.

didn't do anything special but it said it was anhydrous, also i dried the DCM

Upvote

VOTE

Downvote

Dominic Tramonte Follow

If the seal was previously opened then it probably wasn't very anhydrous anymore. Drying that salt is so simple, I do it to a big batch and just put it in the desiccator and use for a long time for everything.

Upvote

VOTE

Downvote

Bob McDonald Follow

Quote from:

Hmm... I'm surprised that chloroformate can survive on a TLC plate. Are you sure that's not hydrolsis product? (carboxylate? alcohol?)

its possible, the spot was very clean and round and quite high up on the plate, i would expect the alcohol or carboxylate to have quite a low Rf value in 4:1 hexane ethyl-acetate.

Upvote

VOTE

Downvote

Deeksha Follow

Did you dry the potassium carbonate? If it was just sitting around in an opened bottle it probably has significant water content.

A solid bake in a vacuum overnight at 150°C+ should do the trick. Store it in a desiccator.

Upvote

VOTE

Downvote

Chr?s Odey Follow

I think the alcohol would run pretty well, Fmoc is rather greasy. I think I. Hydrolyzes into the alcohol and eliminates Co2

Upvote

VOTE

Downvote

David Follow

Quote from:

I don't understand your last response. There are two amines in our discussion. TEA won't react, it's tertiary...

Fmoc protected amines can be deprotected by amine bases the common conditions are 20% piperidine in DMF i just thought TEA would do the same

Upvote

VOTE

Downvote

Dave Howe Follow

Quote from:

I think the alcohol would run pretty well, Fmoc is rather greasy. I think I. Hydrolyzes into the alcohol and eliminates Co2

could it be possible that my product is under the alcohol spot and the reaction is working but not complete?

Upvote

VOTE

Downvote

Chux777 Follow

i'm not overly convinced that this was the problem because TLC showed a very bright spot that corresponds to Fmoc-Cl so there definitely is some in there.

Upvote

VOTE

Downvote