Reactions of o ‐aminonitriles with isocyanates. 1 . A two‐step synthesis of 2,6‐dihydroimidazo[1,2‐ c ]quinazolin‐5‐(3 H )one

The reaction of anthranilonitrile with 2‐chloroethyl isocyanate yields 2‐[3‐(2‐chloroethyl)ureido]benzo‐nitrile ( 6 ) which, upon heating, or treatment with base, undergoes a double cyclization to form 2,6‐dihydroimidazo[1,2‐ c ]quinazolin‐5‐(3 H ) one ( 8 ) in excellent yield. When heated with hydrochloric acid, 6 is converted initially into 2‐(2‐chloroethylamino)‐4 H ‐[3,1]benzoxazin‐4‐one ( 18 ) and further into 3‐(2‐chloroethyl)‐2,4‐(1 H ,3 H )quinazolinedione ( 15 ). The acid‐catalyzed reaction of 2,3‐dihydro‐5 H ‐oxazolo[2,3‐ b ]quinazolin‐5‐one ( 14 ) with nucleophilic reagents yields 3‐substituted 2,4‐(1 H ,3 H )quinazolinediones.