Ionic-liquids-assisted reaction of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with beta-nitrostyrenes

5,6-Diaryl-2,3-dihydro-1H-pyrazolo[1,2-a]pyrazolium tetrafluoroborates (hexafluorophosphate) were unexpectedly synthesized along with expected 1,3-diaryl-2-nitrotetrahydro-1H,5H-pyrazolo[1,2-a]pyrazoles, under the action of 1-nitro-2-(3-nitrophenyl)-ethylene on 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in ionic liquids with the Et2O center dot BF3 catalyst, whereas the same reaction with unsubstituted beta-nitrostyrene produced only 1,3-diaryl-2-nitrotetrahydro-1H,5H-pyrazolo[1,2-a]pyrazole derivatives.