Chemo- and stereoselective synthesis of E-2-(2-acyl-1-tosylvinyl)pyrroles from tosylmethyl isocyanide (TosMIC) and 2-(acylethynyl)pyrroles

Functionalized 2,3′-Bipyrroles and Pyrrolo[1,2-c]imidazoles from Acylethynylpyrroles and Tosylmethylisocyanide

“…At the same time, it was found that the reaction of 2-acylethynylpyrroles with TosMIC, depending on its conditions and substituents in the pyrrole ring, can deliver either pyrrolyl vinyl sulfones [ 40 ] or tosyl/pyrrolyl-capped 1,3-enynes [ 41 ]. In the former case, the reaction proceeds under a long reflux (120 h) in the Et 3 N/MeCN catalytic system, whereas for the easy and rapid (reflux, 1 h) synthesis of tosyl/pyrrolyl-capped 1,3-enynes, the t -BuOK/THF system is employed.…”

Tosyl/pyrrolyl-capped 1,3-enynes via t-BuOK-assisted reaction of TosMIC with acylethynylpyrroles: a new feature of this popular reagent

“…25 We have recently shown that 2-(acylethynyl)pyrroles react with TosMIC in the system Et 3 N/MeCN to chemo-and stereoselectively produce E-2-(2-acyl-1-tosylvinyl)pyrroles (Scheme 2). 26 During optimization of this synthesis we have encountered, to our surprise, a new reaction of this popular reagent: when 1octyl-2-benzoylethynyl-4,5,6,7-tetrahydroindole (1a) reacted with in the KOH/THF system (KOH/THF, reflux, 24 h), instead of the expected vinyl sulfone, 1,3-enyne functionalized with pyrrole, phenyl and tosyl substituents, (E)-1-octyl-2-(3-phenyl-4-tosylbut-3-en-1-yn-1-yl)-4,5,6,7-tetrahydro-1H-indole (2a), was formed in 11% yield (Scheme 3). Although the conversion of the initial acylethynylpyrrole 1a was moderate (21%) and the yield of enyne 2a was low (11%), the reaction was completely selective.…”

“…We have recently shown that 2-(acylethynyl)pyrroles react with TosMIC in the system Et 3 N/MeCN to chemo- and stereoselectively produce E -2-(2-acyl-1-tosylvinyl)pyrroles (Scheme 2). 26…”