[skywolf]

Hi all,

I have a problem with purification of sulfonamide heterocycle containing piperazine moiety. After deprotection of Boc group on piperazine with TFA I must convert the compound from trifluoroacetate to free base and then to acetate (TFA causes the sulfonamide bond to cleave and AcOH is not strong enough to cleave the Boc). However the cleavage of sulfonyl group occurs even with the work-up with acetate. Main problem is, that the compound decomposes itself if it's not in salt form (piperazine part attacks sulfonamide). So I always get a by-product without sulfonyl group (goes to water) and also a by-product with another sulfonyl group attached on piperazine (goes to organic), which are probably formed during work-up. I am looking for some method for the purification to get rid of these derivatives. Can someone give me a method for purification of such salt?

I've tried crystallization (MeOH, EtOH, Et2O, iPrOH) and also flash silicagel with EtOAc but I still get some impurities there. Is there any other method?

Thanks for the help.

[kriggy]

So the problem is during the neutralization or during the making of aceate? could you make different salt for your application instead ? Like hydrochloride?