In the presence of an equimolar amount of triethylamine, 2,5-diphenyl-
3,3,4,4-tetracyanopyrrolidine 1 reacts with vinyl ketones 3 to give l-
2,3,3-tricyano-5-[phenyl(benzylidenamino)methyl] cyclopent-1-enes 6; t
he structure of molecule 6b has been determined by an X-ray study of t
he monocrystal.