The Structure of Crystalline Agnotobenzaldehyde

Abstract: Agnotobenzaldehyde was first reported by Dr. Eugen Bamberger in 1906, from a Zn-promoted reduction of 2-nitrobenzaldehyde. He determined the empirical formula to be C₁₄H₁₂N₂O₅. Subsequent work determined the chemical structure of the solution form by IR and NMR analysis, but the structure of the crystal form remained inconclusive. In the present work, the structure of crystalline agnotobenzaldehyde has been found to be rac-(3R)-1-[(S)-hydroxy(2-nitrophenyl)methyl]-1,3-dihydro-2,1-benzisoxazol-3-ol. Crystals are orthorhombic with the Pbca space group. At 173(2) K, a = 13.8066(14), b = 8.4412(9), c = 22.832(2) Å, and V = 2660.9(5) ų with Z = 8. Poly(O–H⋯) C₄ ⁴(8) chains of alternating intra- and inter-molecular hydrogen bonds form along the b axis. These chains probably affect the regio- and diastereo-specificity of cyclization. Graphical Abstract: The crystalline form of agnotobenzaldehyde has a different molecular structure than the solution form, and features hydrogen bond chains that probably control the stereo- and regio-specificity of the hydroxyl and isoxazole moieties. [Figure not available: see fulltext.].