The mixture of 8.5 g (0.034 mol) of 5,11-dihydro-11-(prop-2-ynyl)-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one, 50 ml of anhydrous dioxan, 1.08 g (0.036 mol) of paraformaldehyde, 2.77 g (0.039 mol) of pyrrolidine and 0.2 g of copper (I) chloride was refluxed for 1 hour with stirring and then, after cooling, evaporated down in a water jet vacuum. The residue was partitioned between water and ethylacetate, the ethylacetate solution obtained was mixed with 2 g of animal charcoal, dried over sodium sulphate, filtered and evaporated down. The residue was purified by column chromatography on silica gel using first ethyl acetate and then dichloromethane/cyclohexane/methanol/conc. ammonia 68/15/15/2 (v/v/v/v) as eluant. The crude product obtained after evaporation of the suitable eluates was recrystallised once more from ethylacetate. Yield: 1.6 g (14% of theory) of colourless crystals, m.p. 153° C.; RF 0.5 (Merck, ready-made TLC plates, silica gel 60 F-254; eluant: dichloromethane/cyclohexane/methanol/conc. ammonia 68/15/15/2 v/v/v/v).
