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 SN1 and intramolecular Michael addition.
[reaction: see text] 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.
Ishikawa
Teruhiko
T
Department of Medical and Bioengineering Science, Graduate School of Natural Science and Technology, Okayama University, Tsushima, Okayama, Japan 700-8530.
Aikawa
Toshiaki
T
Watanabe
Shinichiro
S
Saito
Seiki
S