Efficient synthesis of 1,3,5-trisubstituted (pyrrol-2-yl) acetic acid esters via dual nucleophilic reactions of sulfonamides or carbamate with 4-trimethyl-siloxy-(5E)-hexen-2-ynoates: Lewis acid catalyzed S(N)1 and intramolecular Michael addition

摘要

Carbamates or sulfonamides have proven to regioselectively attack 2-propynyl-allyl hybrid cations, generated by the action of TMSOTf on 4-(trimethylsioxy)hex-5-en-2-ynoates, to afford conjugated 6-aminohex-4-en-2-ynoates in which an intramolecular amino-Michael reaction took place, leading to pyrrole frameworks. In particular, the sulfonamides gave 1-sulfonylpyrroles in one pot.