Synthesis of novel 1,3‐oxazino[6,5‐ b ]indole‐2,4‐(3 H ,9 H )‐dione and 2 H ‐1,3,5‐oxadiazino[3,2‐ a ]indole‐2,4‐(3 H )‐dione from oxindoles

Two novel tricyclic ring systems were designed as serine protease inhibitors and synthesized from oxindoles; the first series, 1,3‐oxazino[6,5‐ b ]indole‐2,4‐(3 H ,9 H )‐diones, were prepared from 2,3‐dihydro‐2‐oxo‐(1 H )‐indole‐3‐carboxamides and phosgene in tetrahydrofuran with triethylamine. The second, a 2 H ‐1,3,5‐oxadiazino[3,2‐ a ]indole‐2,4‐(3 H )‐dione was made using a similar cyclization on 2,3‐dihydro‐2‐oxo‐ N ‐phenyl‐(1 H )‐indole‐1‐carboxamide.