3-[2-(1H-1,3-Benzodiazol-2-yl)ethyl]-1,3-oxazolidin-2-one

In the title compound, C12H13N3O2, the dihedral angle between the oxazolone ring and the benzimidazole unit is 45.0 (5)°, exhibiting a staggered conformation at the Cα—Cβ bond. In the crystal, a strong N—H⋯N hydrogen bond links the molecules into a C(4) chain along the c axis while a C—H⋯O hydrogen-bonding interaction generates a C(5) chain along the a axis, i.e. perpendicular to the other chain.

In the title compound, C 12 H 13 N 3 O 2 , the dihedral angle between the oxazolone ring and the benzimidazole unit is 45.0 (5) , exhibiting a staggered conformation at the C-C bond. In the crystal, a strong N-HÁ Á ÁN hydrogen bond links the molecules into a C(4) chain along the c axis while a C-HÁ Á ÁO hydrogen-bonding interaction generates a C(5) chain along the a axis, i.e. perpendicular to the other chain.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Heterocyclic compounds containing 5-or 6-membered rings are important for their diverse biological activities. In particular, the chemistry of oxazolidinone and benzimidazole has received considerable attention owing to their synthetic and biological importance.
Benzimidazole and oxazolidinone derivatives have been studied for the treatment of different pathologies. Their scaffold has been incorporated into a wide variety of therapeutically interesting compounds that show antibacterial, antifungal, antiviral, antineoplastics and cholinergic activity among others (Niño et al., 2001;Siva Kumar et al., 2010;Zappia et al., 2007).
Furthermore, the introduction in the pharmaceutical market of Linezolid, an oxazolidin-2-one-based antibacterial drug, attracted the interest of the scientists on this scaffold (Brickner et al., 2008). On the basis of some common properties, such as antibacterial activity, of these two classes of heterocyclic compounds, in this study we synthesized the title molecule, in which the benzimidazole ring is linked to an oxazolidinone scaffold, with the aim to obtain a compound having two different moieties in the same molecular entity, and then a synergism of activity.
The one-pot synthetic route employed to obtain the title compound is depicted in Figure 1. Treatment of the commercially available 2-(2-aminoethyl)-benzimidazole dihydrochloride with dibromoethane and potassium carbonate gave the desired product. The proposed mechanism for the synthesis is shown in Figure 2. The nucleophilic attack of the 2-(2-aminoethyl)-benzimidazole primary amine function on the dibromoethane is followed by oxazolidinone ring formation. An excess of potassium carbonate is necessary both to create the basic medium for the N-alkylation and for the formation of the oxazolidinone moiety.
The molecule crystallizes in the centrosymmetric P2 1 /c space group. The asymmetric unit contains one molecule, shown in Figure 3. The dihedral angle between the oxazolone ring and the benzimidazole unit is 45.0 (5)°, exhibiting a staggered conformation at the Cα-Cβ bond. The carbonyl fragment displays pronounced asymmetry at the exo-cyclic angles, being N12-C13-O14 and O14-C13-O15 of 128.4 (1)° and 121.9 (1)°, respectively, because of both electronic and steric factors due to the presence of different atoms bound to C13 (Grassi et al., 2001). The dimensions within the benzimidazole and the oxazolidine moieties are in excellent agreement with those found in the benzimidazole and oxazolidine crystal structures (Totsatitpaisan et al., 2008;Wouters et al., 1997).
Packing analysis of the crystal lattice indicates that the tridimensional molecular arrangement is ruled by many H-bonding interactions. A strong H-bond N1-H1···N8 gives rise to a molecular chain [C(4)] along the c axis ( Figure 4). Another H-bonding interaction C11-H11···O14 generates a chain [C(5)] along the a axis, perpendicular to the previous one.

Refinement
H atoms were located in a difference Fourier map and placed in idealized positions using the riding-model technique, with C-H = 0.93 and 0.97Å for aromatic H and methylene H, respectively, and N-H = 0.86Å, and with U iso (H) = 1.2U eq (C, N).