Formation of N-Methylsulfanylvinyl Derivative in the Synthesis of 2-(Benzo[b]thiophen-3-yl)pyrrole from 3-Acetylbenzo[b]-thiophene Oxime and Acetylene in KOH-DMSO

摘要

While synthesizing 2-(benzo[b]thiophen-3-yl)pyr-role [1] from 3-acetylbenzo[b]thiophene oxime (I) and acetylene in the system potassium hydroxide-dimethyl sulfoxide (Trofimov reaction [2]), apart from 1-vinyl-pyrrole II (yield ～68%) and intermediate NH-pyrrole III (5%), we isolated a small amount (～1%) of 2-(benzo[b]thiophen-3-yl)-1-[(Z)-(2-methylsulfanyl)-vinyl]-1H-pyrrole (IV) (Scheme 1).