supplementary materials

Nitrones have attracted attention of organic chemists as nitrone N⁺–O^- moiety can be treated as an active equivalent of C=O group (Boruah et al. 2003, Freisleben et al. 2002, Saito et al. 2001, Gravestock et al. 2000, Torssell 1988, Floyd 2006). However, only several examples of nitrones bearing a vicinal NH group have been reported so far (Janzen et al. 1997, Clement et al. 1987, Baranowska et al. 1977, Aurich et al. 1976, Rosenberg et al. 1972). As reported, the compounds could be derived from nitriles (Branco et al. 1992), imidoformic acid esters or α-chloroimines (Aurich 1968), hydroxylamines and methylene amines (Aurich 1968, Guimanini et al. 1999), secondary amines (Szantay et al. 1965), and nitroso compounds, from hydroxyguanidines (Southan et al. 1998) or from other nitrones (Warshaw et al.1989). We have succeeded in developing a straightforward way of obtaining nitrones with a vicinal NH group in excellent yields, starting from easily available pyridilides of 3-oxobutanoic acid and nitrosobenzene. The crystal structure analysis of (2Z)-2-anilino-2-[oxido(phenyl)imino]-N-pyridin-2-ylacetamide was performed in order to determine the nature of the interactions between the N⁺–O^- moiety of the title nitrone with the vicinal NH group; this should help us to understand the compound's versatile reactivity towards various diamines. The symmetrically independent part of the unit cell is composed of two 2-anilino-2-[oxido(phenyl)imino]-N-pyridin-2-ylacetamide molecules and a 0.85 methanol molecule disordered between two positions with partial occupancy parameters of 0.586 (7) and 0.264 (7) for O51A—C51A and O51B—C51B, respectively. The conformation of the two symetrically independent nitrone molecules is shown in Figs. 1a and 1 b. No appreciable differences can be observed between the bond lengths and angles of the independent nitrone molecules and they are comparable with the values reported in the literature (Allen et al. 1987). The planarity of the C–C=N⁺→(O^-) part with Z configuration, in respect of N12–C10 double bond, observed for both symmetrically independent molecules is the most interesting feature of the investigated molecules, from the geometrical point of view. The O13—N12—C10—N11 and O13—N12—C10—C8 torsion angles are 2.6° and -174.3°, respectively for molecule A and -4.1° and 174.4°, respectively for molecule B. Significant torsion angles observed for nitrone molecules A and B are compared in Table 1. A l l aryl rings are twisted against each other: 〈 (C14···C19/N1···C6) = 68.0 (1)° for A and 53.8 (1)° for B; 〈 (C20···C25/N1···C6) = 75.5 (1)° for A and 66.4 (1)° for B. The crystal packing (Fig. 2) is controlled by N—H···O, N—H···N and O—H···O hydrogen bonds and weak van der Waals interactions (Table 2). The two N atoms (N7 and N11) in each molecule of the title compound are involved in the hydrogen bonds as donors forming two intra- and one intermolecular hydrogen bonds (Table 2). The intermolecular N11—H11···N1 interactions are relatively weak, with donor–acceptor distances of 3.095 (3) Å and 3.056 (3) Å due to simultaneous donor participation in intramolecular N11—H11···O13 interactions.