Crystal structure of pirfenidone (5-methyl-1-phenyl-1H-pyridin-2-one): an active pharmaceutical ingredient (API)

The crystal structure of pirfenidone, C₁₂H₁₁NO [alternative name: 5-methyl-1-phenyl-pyridin-2(1H)-one], an active pharmaceutical ingredient (API) approved in Europe and Japan for the treatment of Idiopathic pulmonary fibrosis (IPF), is reported here for the first time. It was crystallized from toluene by the temperature gradient technique, and crystallizes in the chiral monoclinic space group P2₁. The phenyl and pyridone rings are inclined to each other by 50.30 (11)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds involving the same acceptor atom, forming undulating layers lying parallel to the ab plane.