3 41-Aryl-3-(2-ethoxycarbonylphenyl)carbodiimides 2, obtained from aza-Wittig reactions of iminophosphorane 1 with aryl isocyanates, reacted with primary diamines in 1:1 and 2:1 molar ratio under mild conditions to give selectively the regioisomers 3-aminoalkyl-2-arylaminoquinazolin-4(3H)-ones 3 and 3,3'-disubstituted bis-2-arylaminoquinazolin-4(3H)-ones 4 in good yields, respectively. To fully characterize the regioselectivity of aza-Wittig reactions of 1-aryl-3-(2-ethoxycarbonylphenyl)carbo-diimides with primary diamines, crystals of 4e were obtained, and its structure was determined by X-ray crystallography.