We often had a similar problem. Sometimes solvent change helps: ethanol - ethyl acetate. If amine is more unstable, it is necessary to work in inert atmosphere, as with organometallic compounds. We use reversing ("back way") filtration in inert atmosphere, to press amine solution to the next reactor for the following transformation to more stable product.

If no problem with salt, directly prepare salt instead of distillation.

The alkyl group is in fact an ethyl ester... besides, the salt I obtain (HCl) is colored.

We often had a similar problem. Sometimes solvent change helps: ethanol - ethyl acetate. If amine is more unstable, it is necessary to work in inert atmosphere, as with organometallic compounds. We use reversing ("back way") filtration in inert atmosphere, to press amine solution to the next reactor for the following transformation to more stable product.

I had sucha problem before with another amine. The suggestion givem by Dr Inna is the answer: work under inert atmosphere.

As a matter of fact, this arylamine should be prepared in bulk for various acylations.

Certainly, you can evaporate this amine in atmosphere of argon and store it under argon for short time. We have the special equipment for weighing unstable substances in inert atmosphere in our laboratory. Have you such equipment too? But the best strategy is to carry out a series of experiments for scaffold synthesis on the basis of unstable compounds at once, dosing a solution of amine to such quantity of reactors what is necessary.

We have thought of reduction using Fe and Acetic acid/ethanol. This way, the HCl salt is prepared promptly. Thank you all for your suggestions.

It certainly would be a good idea, had the compound not crash out in ether... The most doable way was to filer the solution over celite and into a flask that contained excess amount of HCl in dioxain that has effectively quenched the oxidation.

I like the idea on the diethylether blanket, easy, cheap.... I do like inert gaz, argon is great as it is heavy and really form a blanket. Nitrogen is also good but I would use it is a glove box or at least a bag.

We are facing amine stability. From nitro to amine reduction in NaSH we are getting only 70%pure compound, due to amine decomposing fast. let me give solution.

The reaction and removal of solvent both have carried out under inert atmosphere. Air oxidation will change the colour of simple amine like aniline. So one of the hole is given for inert gas flow. It will remove oxygen by becoming a blanket over your reaction mixture. Please also reduce the temperature and apply high vacuum for separation. Also you have to purge the solvent atleast for 15 minutes for avoiding the presence of oxygen in solvent voids.