Crystal structure of 2-{[5-(methylsulfanyl)-4-phenyl-4H-1,2,4-triazol-3-yl]methyl}benzo[d]thiazole

In the crystal structure of the title compound, the triazole ring exhibits interplanar angles of ca 64 and 77° with the phenyl and benzothiazole planes, respectively. The packing involves three borderline C—H⋯N contacts and a pairing of the triazole rings across an inversion centre.


Chemical context
Benzothiazoles and their derivatives are among the most important heterocyclic compounds in medicinal chemistry and are essential to many natural products and therapeutic preparations (Bonde et al., 2015).The derivatives involve a wide range of structural variants (Rana et al., 2008), and their pharmacological qualities are reflected in the extensive hunt for new therapeutically active compounds (Wang et al., 2009), which represents a rapidly developing research area (Abdallah et al., 2023a,b;Ammazzalorso et al., 2020;Gill et al., 2015).In particular, several substances based on benzothiazole derivatives have been adapted and/or further developed for clinical practice to treat a wide range of diseases with great therapeutic efficacy (Huang et al., 2009;Seenaiah et al., 2014).
As part of our development of synthetic methods for the preparation of benzothiazole-based heterocycles and other pharmaceutically interesting heterocycles (Ahmed et al., 2022;Yakout et al., 1999), we recently described the synthesis and biological activity of a series of 2-pyrimidyl-and 2-pyridylbenzothiazole derivatives with encouraging cytotoxic activity (Azzam et al. 2020a(Azzam et al. ,b,c, 2022a,b),b).
As a continuation of this programme, related to our recent results (Elgemeie et al., 2020(Elgemeie et al., , 2022;;Metwally et al., 2022a,b), the purpose of the present study was to design and synthesize benzothiazolyl-triazole hybrids.The synthesis of our target benzothiazole-2-triazole derivative 5 was achieved by reacting the 2-benzothiazolyl acetohydrazide 1 with phenyl isothiocyanate 2 in the presence of sodium ethoxide, followed by addition of methyl iodide to give 5 in good yield (Fig. 1).The formation of 5 is assumed to proceed via initial formation of adduct 4, with subsequent elimination of water.In order to establish the structure of the product unambiguously, its crystal structure was determined and is reported here.

Structural commentary
The structure of compound 5 is shown in Fig. 2. Bond lengths and angles may be generally regarded as normal; e.g. the two S2-C bond lengths differ appreciably, reflecting the different hybridizations of C10 and C11.One exception may be the angle C2-C8-C9 at the methylene group, which is rather wide at 114.28 (4) � (see below).A selection, mostly involving the heteroatoms, is presented in Table 1.The triazole ring subtends interplanar angles of 63.86 (2) and 76.96 (2) � with the phenyl and benzothiazole planes, respectively.The intramolecular distance S1� � �N1 is 3.4819 (5) A ˚, far too long to represent any significant interaction, in contrast to the value of 2.7570 (8) A ˚that we recently observed for the intramolecular S� � �N imine contact in N- [3-(benzo[d]thiazol-2-yl)-6-bromo-2Hchromen-2-ylidene]-4-methylbenzenamine (Abdallah et al., 2023a).

Supramolecular features
The molecular packing displays few significant features.There are three borderline C-H� � �N interactions (Table 2), two of which (the first and third in Table 2) connect the molecules by translation to form thick layers parallel to the ac plane (Fig. 3).The triazole rings are associated in pairs (presumably representing a �-� interaction) via the operator 1 À x, À y, 1 À z, with intercentroid, interplanar and offset distances of 3.3222 (3), 3.1852 (2) and 0.94 A ˚, respectively.This feature is reinforced by the other C-H� � �N interaction, which involves the same operator.

Database survey
The searches employed the routine ConQuest (Bruno et al., 2002), part of Version 2022.3.0 of the Cambridge Database (Groom et al., 2016).
Only one other structure containing both a triazole and a benzo Reaction scheme for the synthesis of 5.
To see if the C-C-C angle at the methylene group of 5 is unusually wide, a search was performed for all structures with two five-membered rings connected across a methylene group; the one restriction was that both of the outer carbon atoms should be three-coordinated.This led (excluding a few clear outliers) to 445 values in the range 106-122 � , with a mean value of 114 (5) � .However, restricting one ring to be a C2substituted thiazole gave only three hits, with four values of 109.6-112.9� for the angle at the methylene groups.These all involved two planar ring systems of the benzo[d]thiazole type, but with different heteroatoms in some cases (HANSIB and HANSOH, Dauer et al., 2017;KONTAK, Dauer & Stalke, 2014).

Synthesis and crystallization
A mixture of 2-benzothiazolyl acetohydrazide 1 (0.01 mol) and phenyl isothiocyanate 2 (0.01 mol) was stirred for 30 min in ethanol (25 mL) in the presence of sodium ethoxide (0.01 mol).After cooling, methyl iodide (0.015 mol) was added.The reaction mixture was stirred for 30 min at room temperature, then refluxed for 1 h.The resulting precipitate was filtered off, washed with water, dried, and recrystallized from ethanol.The title compound was isolated as a white solid; yield 75%; m.p. 429 K; IR (KBr, cm

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3.The methyl group was included as an idealized rigid group allowed to rotate but not tip (C-H = 0.98 A ˚, H-C-H = 109.5� ).Other hydrogen atoms were included using a riding model starting from calculated positions (C-H aromatic = 0.95 A ˚, C-H methylene = 0.99 A ˚).The U(H) values were fixed at 1.5 � U eq of the parent carbon atoms for the methyl group and 1.2 � U eq for other hydrogens., 1994); software used to prepare material for publication: SHELXL2019/3 (Sheldrick, 2015b).

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) -0.6560 (0.0019) x -4.

Figure 3
Figure 3 Packing diagram of compound 5, showing the layer structure parallel to ac in the region y ' 0.25.Thick dashed bonds represent 'weak' C-H� � �N hydrogen bonds.The labelled atoms indicate the asymmetric unit.

Table 3
Experimental details.