3-Ethoxy-5-phenyl-1 H -1,2,4-triazole

The title compound, C 10 H 11 N 3 O, crystallizes in the triclinic space group P 1 with Z 0 = 2. The two independent molecules ( A and B ) differ in the orientation of the phenyl rings with respect to the plane of the triazine ring, with an interplanar angle of 11.45 (6) (cid:2) in molecule A and 19.71 (5) (cid:2) in molecule B , in the opposite sense. In the crystal, classical N—H (cid:3) (cid:3) (cid:3) N hydrogen bonds cross-link the molecules to form chains parallel to the b axis. Two additional ‘weak’ C— H (cid:3) (cid:3) (cid:3) O hydrogen bonds link the chains to form layers parallel to (101). the of various antimetabolic cyanoketene N , S -acetals cyanoketene S , S -acetals , 2017 cyanoketene N , N acetals of ( E This gave a product whose mass spectrum was not consistent with the proposed pyrazole structure ( 3 ). Other spectroscopic measurements did not allow us to identify the product unambiguously and therefore the X-ray crystal structure was determined, conﬁrming the exclusive presence of the triazole derivative ( 7 ) as sole product in the solid state. The formation of ( 7 ) is assumed to proceed via initial addition of the basic N atom of hydrazine to the double bond of ( 1 ), followed by formation of adduct ( 4 ) and elimination of ethyl cyanoacetate. From adduct ( 4 ), the favoured, kinetically and thermodynamically controlled product ( 7 ) is formed.

The title compound, C 10 H 11 N 3 O, crystallizes in the triclinic space group P1 with Z 0 = 2. The two independent molecules (A and B) differ in the orientation of the phenyl rings with respect to the plane of the triazine ring, with an interplanar angle of 11.45 (6) in molecule A and 19.71 (5) in molecule B, in the opposite sense. In the crystal, classical N-HÁ Á ÁN hydrogen bonds cross-link the molecules to form chains parallel to the b axis. Two additional 'weak' C-HÁ Á ÁO hydrogen bonds link the chains to form layers parallel to (101).

Structure description
Cyanoketene S,S-acetals and cyanoketene N,S-acetals are important synthetic intermediates (Elgemeie et al., 2015(Elgemeie et al., , 2016) that have been used as building blocks to assemble a wide range of heterocyclic compounds (Azzam et al. 2017a(Azzam et al. ,b, 2019; they are also of general interest in medicinal chemistry (Abu-Zaied & Elgemeie, 2017Elgemeie et al. 2017c). Recently, we have reported the synthesis of various antimetabolic agents starting from cyanoketene N,S-acetals (Elgemeie et al. 2006(Elgemeie et al. , 2009, cyanoketene S,S-acetals (Elgemeie et al., 2003a(Elgemeie et al., , 2017d, and cyanoketene N,Nacetals (Elgemeie et al., 2003b). As a part of this programme, the reaction of (E)-ethyl 3-benzamido-2-cyano-3-(methylthio)acrylate (1) with hydrazine was investigated (Fig. 1). This gave a product whose mass spectrum was not consistent with the proposed pyrazole structure (3). Other spectroscopic measurements did not allow us to identify the product unambiguously and therefore the X-ray crystal structure was determined, confirming the exclusive presence of the triazole derivative (7) as sole product in the solid state. The formation of (7) is assumed to proceed via initial addition of the basic N atom of hydrazine to the double bond of (1), followed by formation of adduct (4) and elimination of ethyl cyanoacetate. From adduct (4), the favoured, kinetically and thermodynamically controlled product (7) is formed. data reports Compound (7) crystallizes with two molecules (A and B) in the asymmetric unit, linked by the hydrogen bond N1-H01Á Á ÁN4 0 (Table 1 and Fig. 2). The triazine rings of the two molecules subtend an interplanar angle of 74.75 (4) . The asymmetric unit was chosen so that the molecules are linked by a hydrogen bond, but the best least-squares fit (r.m.s. deviation 0.057 Å excluding C12, C13, C15, C16) is obtained when one molecule is inverted (Fig. 3). The molecules differ in the orientation of the phenyl ring, whereby the interplanar angle to the triazine ring is 11.45 (6) in molecule A (unprimed atoms) but 19.71 (5) in molecule B (in the opposite sense).

Synthesis and crystallization
Hydrazine hydrate (1 mmol) was added to a solution of (E)-ethyl 3-benzamido-2-cyano-3-(methylthio)acrylate (1) (1 mmol) in ethanol (20 ml) containing a few drops of piperidine. The mixture was heated under reflux with continuous stirring for 2 h, then poured onto ice. The solid product was filtered off, dried and recrystallized from ethanol to afford compound (7)

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Table 1 Hydrogen-bond geometry (Å , ).

Figure 2
A view of the molecular structures of the two independent molecules of compound (7), with the atom numbering. Displacement ellipsoids are drawn at the 50% probability level. The dashed line indicates a classical hydrogen bond (Table 1).

Figure 3
Least-squares fit of all non-hydrogen atoms, except C12, C13, C15 and C16, of inverted molecule A (dashed lines) on molecule B.

data-1
IUCrData ( Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) 7.6131 (