The Conversion of a Pyrrole Trimer Derivative into a 4,5,6,7-Tetrahydro-4-(pyrrol-2-yl)indol-7-yltosylaminoindole.

Vilsmeier formyl­ation of trans-1-(4-methyl­phenyl­sulfonyl)-2,5-bis(pyrrol-2-yl)­pyrrolidine leads to cleavage of the central ring then a reclosure resulting in the formation of trans-N-[2-formyl-4-(5-formyl­pyrrol-2-yl)-4,5,6,7-tetra­hydro­indol-7-yl]­toluene­sulfon­amide, C21H21N3O4S.