Reactions of o‐aminonitriles with isocyanates. 1. A two‐step synthesis of 2,6‐dihydroimidazo[1,2‐c]quinazolin‐5‐(3H)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‐(3H) one (8) in excellent yield. When heated with hydrochloric acid, 6 is converted initially into 2‐(2‐chloroethylamino)‐4H‐[3,1]benzoxazin‐4‐one (18) and further into 3‐(2‐chloroethyl)‐2,4‐(1H,3H)quinazolinedione (15). The acid‐catalyzed reaction of 2,3‐dihydro‐5H‐oxazolo[2,3‐b]quinazolin‐5‐one (14) with nucleophilic reagents yields 3‐substituted 2,4‐(1H,3H)quinazolinediones.