The title compound was prepared as previously reported via double lithiation of 4-pivaloylaminopyridine with n-BuLi (2.1 mole equivalents) in anhydrous THF at 0°C for 3 h followed by a reaction with carbon monoxide. The crude product obtained was purified by crystallization from ethyl acetate to give the title compound in 65% yield as colourless crystals [1].

Synthesis of azaindoles is of great interest due to their growing biological applications [2]. The asymmetric unit consists of one molecule of C₁₁H₁₄N₂O₂. In the crystal structure, the hydroxyl group accepts one N—H⋯O hydrogen bond from a neighbouring molecule (N1—H1⋯O2 angle = 169.63°, N1⋯O2 distance = 2.851 Å) and donates one O—H⋯N bond to another molecule (O2—H2⋯N2 angle = 172.48°, O2⋯N2 distance = 2.710 Å) leading to a 3-D network. An extremely weak C—H⋯O contact is also observed (C5—H5⋯O1 angle = 173.13°, C⋯O distance = 3.362 Å) resulting in R²₂(9) graph set descriptor for this motif [3] between two molecules. The shortest C—H⋯O contact in the related 3-isopropyl-1-methyl-1,3-dihydro-2H-pyrrolo[3,2-c]pyridin-2-one [4] involves a tertiary C atom (C—H⋯O angle = 144.18° and C⋯O distance = 3.292 Å).

H atoms were placed in calculated positions and refined using a riding model, with U_iso(H) set to 1.2U_eq(C) and C—H and N—H distance of 0.93 and 0.86 Å respectively. The exceptions were the methyl (C—H = 0.96 Å) and hydroxyl (O—H = 0.86 Å) groups which were allowed to rotate around the C—C bond (HFIX 137 in SHELX [6]) and C—O bond (HFIX 147), with U_iso(H) set to 1.5U_eq(C/O).

The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for its funding for this research through the research group project RGP-VPP-239 and to Cardiff University for continued support.