Extensive Intramolecular and Intermolecular Interactions in Two Quaternary Salts of the Pyridoxal Oxime

Abstract

Two derivatives of pyridoxal oxime (1) were prepared by quaternization of pyridoxal oxime with phenacyl bromide and 2-methoxyphenacyl bromide. The crystal structures of the 1-phenacyl-3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-2-methylpyridinium bromide (2) and the novel 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethyl-2-methyl-1-(2 0 -methoxyphenacyl) pyridinium bromide (3) have been determined by X-ray diffraction method. The conformation of these two pyridoxal oxime phenacyl derivatives is locked by numerous intramolecular hydrogen bonds. The O-HÁÁÁBr, C-HÁÁÁBr and C-HÁÁÁO hydrogen bonds in 2 and 3 form complex three-dimensional network. Supramolecular structure of 3 also contains C-HÁÁÁp and pÁÁÁp interactions which link neighbouring cations.

An Efficient Synthesis of Pyridoxal Oxime Derivatives under Microwave Irradiation

“…However, sum of the endocyclic bond angles is 720°, as expected for aromatic six-membered ring. The bond lengths and angles agree quite closely with equivalent ones in structures of 3-hydroxy-4-hydroxyiminomethyl-5-hydroxymethylpyridinium derivatives [16,17]. The C2 ring atom is in synclinal position with respect to the C11 atom of the phenacyl moiety [C2−N1−C10−C11 = 77.2(3)°].…”