[wildfyr]

Its just acid/base chemistry, that conversion should be self evident. Think about what happens when you basify aminothiophene oxalate salt.

[rolnor]

My guess is its the free aminothiophene carboxylic acid that decarboxylates, this is the case for malonic acids although this is another, cyclic mekanism. Try to monitor the reaction, TLC should be possible to use if you don not have LC-MS.

[Sach]

So rolnor, you don't agree that decarboxylation is caused by NaOH followed by the heat?

[rolnor]

I am not sure about that, I can be wrong. You could monitor the reaction by TLC, maybe ethyl acetate/hexane 1:1. Then you can see where the decarboxylation step occurs

[Sach]

Ok thank you