The three-component reaction of 3-phenyl-1-azabicyclo[1.1.0]butane (1a) with 2,3-dicyanofumarates (DCFM) and primary aromatic amines in dichloromethane at room temperature yielded mixtures of (Z)-2-arylamino-3-cyanofumarates (7) and the corresponding (E)-2-(azetidin-1-yl)-3-cyanomaleates (6) and (9). In the case of anisidine (8d), higher oligomers containing three or four azetidine residues, e.g. 10a, were also formed. With more nucleophilic aliphatic amines, only 1:1 adducts of type 7 were obtained. The reaction course can be rationalized by the formation of intermediate zwitterions (11) via addition of the N-nucleophiles onto DCFM. The results show that the nucleophilicity of 1a toward DCFM is lower than that of aliphatic amines but exceeds that of aromatic amines.