2-(2-Hydroxyethyl)-3-[(2-hydroxyethyl)imino]isoindolin-1-one

In the crystal structure of the title compound, C12H14N2O3, molecules are packed into layers parallel to (100). Each layer contains centrosymmetric dimers formed by a pair of strong O—H⋯N hydrogen bonds with an R 2 2(10) motif, while strong O—H⋯O hydrogen bonds forming C(10) chains connect molecules into a two-dimensional network. Additional stabilization is supplied by weak C—H⋯O hydrogen bonds and weak π–π stacking interactions with centroid–centroid distances in the range 3.4220 (7)–3.9616 (7) Å.

In the crystal structure of the title compound, C 12 H 14 N 2 O 3 , molecules are packed into layers parallel to (100). Each layer contains centrosymmetric dimers formed by a pair of strong O-HÁ Á ÁN hydrogen bonds with an R 2 2 (10) motif, while strong O-HÁ Á ÁO hydrogen bonds forming C(10) chains connect molecules into a two-dimensional network. Additional stabilization is supplied by weak C-HÁ Á ÁO hydrogen bonds and weakstacking interactions with centroid-centroid distances in the range 3.4220 (7)-3.9616 (7) Å .

Related literature
For background to the chemical and electrochemical properties of aromatic dicarbonyl compounds, see: Zuman (2004). For the use of reactions between phthalaldehyde and nucleophiles for the fluorimetric determination of amino acids, see: Roth (1971); For other structures isolated from systems in which kolamine was reacted with phthalaldehyde, see: Urban (2007aUrban ( , 2007b. For hydrogen bonding and graph-set motifs, see: Desiraju & Steiner (1999);Etter et al. (1990). For the extinction correction, see: Becker & Coppens (1974 Table 1 Hydrogen-bond geometry (Å , ).

Comment
In the course of the authors' investigations on the chemical and electrochemical properties of aromatic dicarbonyl compounds (Zuman, 2004) the reactivity of phthalaldehyde with nucleophiles has been studied. The reaction between phthalaldehyde and nucleophiles is important because namely the reaction of phthalaldehyde with amino acids is used for the fluorimetric determination of the latter substances. The fluorescence is substantially enhanced if another, stronger nucleophile is added in excess to phthalaldehyde prior to its reaction with an amino acid (Roth, 1971). Despite of the practical application of this reaction the chemical mechanism of this a rather complex process is still not fully understood. In order to elucidate the reaction steps we started to study the reactions between phthalaldehyde and a stronger nucleophile [2-aminoethanol (kolamine)] before adding an amino acid.
The interaction between phthalaldehyde and a nucleophile seems to be crucial because it is strongly dependent on a medium, on the sequence of the added chemicals (kolamine prior to phthalaldehyde or vice versa) as well as on the way, e.g. its speed, of their mixing as follows from our preliminary studies (Urban et al., 2007a,b). The aim of this study is to investigate the reaction pathway by isolation of some intermediate products before adding an amino acid.
As the first studied nucleophile we have used 2-aminoethanol (kolamine). A previously applied procedure (Urban et al. 2007a,b) involving the addition reaction in non-aqueous acetonitrile when kolamine was added dropwise led to the isolation of two products. In contrast to these previous studies the reaction presented here proceeded in 0.1 M HCl and yielded the title compound that is different from those described by Urban et al. (2007a,b;see Fig. 5). The study that aims to explain this difference in the reactions paths in various evironments is under progress as well as the study of the detailed reaction pathway of the subsequent reaction with an amino acid.
The molecular structure of the title compound is shown in Fig. 1. In the crystal structure, the most important intermolecular interactions between the molecules are strong (Desiraju & Steiner, 1999) O-H···N and O-H···O hydrogen bonds (Table   1). The O3-H3···N2 i [symmetry codes as in Table 1] hydrogen bonds are involved in the formation of dimers with the graph set motif R 2 2 (10) (Etter et al., 1990; Fig. 2, Fig. 3). These dimers are located on crystallographic inversion centers. Each such a dimer is interconnected to another one displaced by 0, 1/2, 1/2 via O-H···O hydrogen bond with the motif C(10) (Fig. 3). These chains together with the above mentioned dimers are interconnected by other symmetry-equivalent O-H···O hydrogen bonds and form a two-dimensional pattern (Fig. 4) that is parallel to (100). There are also week C-H···O hydrogen bonds and it is interesting that the carbonyl oxygen O1 is involved in a weak C-H···O hydrogen bonding.
There are also π-π stacking interactions between the aromatic rings of the title molecule as indicates their stacking along the b axes in the approximate distance b/2=3.57334 (3) Å. Specifically, the distances between the centroids of the pyrrole rings equal to 3.4220 (7) and 3.8779 (7) Å for the rings displaced by 1/2 -x, 3/2 -y, z and 1/2 -x,1/2 -y, z, respectively.
supplementary materials sup-2 The attempts at crystallizations of other isolated compounds failed and therefore their molecular structures were assigned by 1 H and 13 C NMR spectrometry (Fig. 5). The spectra were taken on the NMR spectrometer Varian 300 MHz at frequencies 229.970 and 75.434 MHz for 1 H and 13 C, respectively. as well as chloroform -toluene-n-hexane (2:1:1 v/v) microcrystallne form has been obtained at best. The structure of (II) was inferred from the NMR spectra 1 H and 13 C. The isolated compound (II) is not stable, it decomposes, especially in acid medium (pH~4), into the compound (I) and 2-(2-hydroxyethyl)-2,3-dihydro-1H-benzo[c]pyrrol-1-one (III) -see Scheme 2. The NMR spectrum of (III) is the same as that of 2-(2-hydroxyethyl)-2,3-dihydro-1H-benzo[c]pyrrol-1-one the crystal structure of which has already been determined (Urban, 1997a).

Refinement
All the hydrogen atoms could be distinguished in the electron-density difference maps. Furthermore, all the hydrogen atoms could have been refined yielding good geometry. Nevertheless, all the H atoms attached to the carbon atoms have been constrained in the riding motion approximation while the coordination parameters of the hydroxyl H atoms that are involved in the strong hydrogen bonds have been freely refined. The values of the constraints are: C aryl -H=0.93, C methylene -H=0.97 Å. U iso H=1.2U eq C aryl /C methylene /O hydroxyl . Fig. 1. The title molecule with the atomic numbering scheme. The displacement ellipsoids are shown at the 50% probability level.     (15)