1-Phenyl-3H-2,3-benzodiazepin-4(5H)-one

The seven-membered ring in the title compound, C₁₅H₁₂N₂O, adopts a boat-shaped conformation (with the methyl­ene C atom as the prow and the double-bond C=N pair of atoms as the stern). In the crystal, adjacent mol­ecules are linked by an N—H...O hydrogen bond to generate helical chains running along the a axis of the ortho­rhom­bic unit cell.