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Mike Miller

Reductive amination, DCE

David Vanderschel  Follow
Quote from:
A. F. Abdel-Magid, K. G. Carson, B. D. Harris, C. A. Maryanoff, R. D. Shah, J. Org. Chem., 1996, 61, 3849-3862 "

I'm sure it says somewhere else in that paper that they wanted to avoid DCM because it can (very slowly) react with some amines. This is from memory though, I could be wrong.

I've found this reaction generally works very well, but we have occasionally had reactions that were much cleaner in THF than DCE. Also, we've generally found the yields are better if you prepare the triacetoxyborohydride in situ using NaBH4 + 3 eq AcOH rather than using commercially supplied NaBH(OAc)3.

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Bob McDonald  Follow
Quote from:
Quote from:
I'm sure it says somewhere else in that paper that they wanted to avoid DCM because it can (very slowly) react with some amines. This is from memory though, I could be wrong.

That was my first thought as well. I haven't done this reaction, but I also wondered whether the reaction might be moderately heated as an option?

Ah, that would explain some of the faint dots on the TLC. I heat mine to 30°C and it seems to help speed up the reaction. I also found that if I have it extremely dry, the reaction doesn't work as well.

I think I'll use dry THF (depending on solubility), as I don't want to buy in 1,2-dichloroethane for one one small step in my synthesis. I'll try making the triacetoxyborohydride in situ as well. The commercial triacetoxyborohydride is very hygroscopic, which is a pain when trying to slowly add the powder.

Cheers for the help guys

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Bipolar & Mood Disorders  Follow
Quote from:
I'm sure it says somewhere else in that paper that they wanted to avoid DCM because it can (very slowly) react with some amines. This is from memory though, I could be wrong.

That was my first thought as well. I haven't done this reaction, but I also wondered whether the reaction might be moderately heated as an option?

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Bill Nugent  Follow
I have many times found that people use the solvent that was used in the original paper but many other solvents can often also be used with good result.

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