N-(Prop-2-yn-1-yl)-1,3-benzothiazol-2-amine

In the title compound, C10H8N2S, the 2-aminobenzothiazole and propyne groups are not coplanar [dihedral angle = 71.51 (1)°]. The crystal structure is stabilized by strong intermolecular N—H⋯N hydrogen bonds and C—H⋯C, C—H⋯π and F-type aromatic–aromatic [centroid–centroid distance = 3.7826 (12) Å] interactions are also observed.

AA and MKS are thankful to the University Grant Commission (scheme No. 34-311/2008), New Delhi, and Banaras Hindu University (BHU), Varanasi, India, respectively, for financial assistance. The authors are highly thankful to the department of Chemistry, Banaras Hindu University, for providing the single-crystal X-ray data.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZJ2020).

Comment
Heterocyclic compounds containing nitrogen, sulfur, oxygen etc have immense importance especially in pharmaceutical industry. Most of the modern drugs contain one or more heteroatom in their scaffold. Further, oxidation of nitrogen in heterocycle plays key role in bioactivity of these scaffolds (Xuan, et al., 2001). It is well documented that benzothiazole and benzimidazole derivatives show wide range of biological activities including antilipidemic (Caroti, et al., 1989), antimicrobial (Kus, et al., 1996), antiviral (Paget, et al., 1969) anti-inflammatory and analgesic properties (Da Settimo, et al., 1992).
Moreover, 2-aminobenzimidazole/benzothiazole derivatives are common intermediate for the synthesis of various drugs.
In the title compound, the C7-N2 single bond (1.342 Å) is shorter than normal C-N bond (1.47 Å) suggesting a delocalized double bond in benzothiazole moiety. Further, N2-C8 bond (1.438 Å) is also shorter than a standard C-N bond distance due to delocalization of electrons. Again, it is evident from the crystal structure that the title compound is stabilized by strong intermolecular N-H···N hydrogen bonding as well as C-H···π interactions and aromatic π···π stacking interaction resulting in the formation of supramolecular arrangement in the cystal as seen in the crystal packing along b axis ( Figure 2, Table 1). The intermolecular hydrogen bond distance between N2···N1 (2.91 Å) is shorter than N···N average bond range 3.15 Å, suggesting strong hydrogen bonding (Mingos & Braga, 2004).
In the cystal packing two benzothiazole skeletons are arranged in an antiparallel fashion by F-type aromatic-aromatic interactions and form a dimer, the ring A and C of an benzothiazole skeleton stacks with the ring C and A of another adjacent benzothiazole skeleton, respectively. The distance of CgA and CgC is 3.783 Å, where CgA and CgC are the center of ring A and C, respectively and the centroid -centroid distance between two adjacent benzothiazole ring is 3.879Å (

Experimental
The synthesis of the title compound was carried out according to the published procedure (Lilienkampf, et al., 2009). Briefly, to a solution of 2-aminobenzothaizole (0.90 g, 6 mmol) in dry acetone was added anhydrous K 2 CO 3 (4.97 g m, 32 mmol) and reaction mixture was further refluxed for 15-30 minutes. Subsequently, KI (0.50 g m, 3 mmol) and propargyl bromide (0.64 ml, 7.2 mmol) were added and further refluxed the reaction mixture for 18 hrs. The reaction mixture was cooled, filtered, and the filtrate was evaporated in vacuo to give the product which was purified by column chromatography using hexane and dichloromethane (65:35) as eluent. The product was crystallized from hexane:dichloromethane (1:1). The light pink colored crystals were obtained by slow evaporation of solvent at room temperature in several days. Yield = 20%.

Refinement
All H atoms were located from difference Fourier map (range of C-H = 0.87 -0.98 Å and N-H = 0.87 Å) and allowed to refine freely.

N-(Prop-2-yn-1-yl)-1,3-benzothiazol-2-amine
where P = ( Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.