observed

havaittu (en-past of)

http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Acta/al_acta_30_01.pdf Aldrichimica Acta Volume 30 No 4 (pdf) from http://www.sigmaaldrich.com/chemistry/chemical-synthesis/learning-center/aldrichimica-acta.html Sigma-Aldrich

N-substituted pyrroles are much less reactive than the other 5-membered 1,3-dienes; no reaction was observed between N-(trimethylsilyl) pyrrole or N-benzylpyrrole with Smith’s diene (4) under thermal or high pressure (4 days at 14 kbar) conditions, even in the presence of Lewis acids.