I need to make a reaction of amine (R-NH2) with ester in the presence of NaH in order to obtain amide (R-NH-CO-R'-NH2). The point is that ester also carries the NH2 group (H2N-R'-CO2-R''). How to protect the amino group to avoid self-reaction? I think that formation of Schiff base may work (R'''-CH=N-R'-CO2-R'') but need to be sure if the said Schiff base will be stable in the following reactions:
1. R'''-CH=N-R'-CO2-R' + R-NH2 --(NaH, THF)--> R'''-CH=N-R'-CO-NH-R
2. R'''-CH=N-R'-CO-NH-R --(deprotection - HOW?)--> H2N-R'-CO-NH-R
"STABASE" protection is exactly suitable for aminoacids, deprotection by OH-, AcOH and HCl, probably by F- : http://www.sciencedirect.com/science/article/pii/S0040403901904393
1,2-Bis(chlorodimethylsilyl)ethane available from ALFA catalog #L02570 , ~$100/100g
Boc2O its a good option
http://www.commonorganicchemistry.com/Rxn_Pages/Boc_Protection/Boc_Protection_Index.htm
I agree with Antoni, Boc2O is a very nice choice for protection, I already tried it with aminoacids, just mix in THF, and for deprotection later, HCl is a good choice
The self condensation can be resolved by increasing the distance between the parties (solvents does) and increasing equivalents of amine, competition between them (hint: perhaps this is the solvent) can also use a weaker base if applicable !
And our colleague said protection anhydride before use (distill it several times to remove acetic acid)
hugs
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