Crystal structure of N-[6-amino-5-(benzo[d]thiazol-2-yl)-3-cyano-4-methylsulfanyl-2-oxo-1,2-dihydropyridin-1-yl]-4-methylbenzenesulfonamide dimethylformamide monosolvate

In the title compound, the toluenesulfonamide ring and the combined ring system involving the pyridone and benzothiazole rings subtend an interplanar angle of 39.86 (4)°. The pyridone and benzothiazyl rings are linked by an intramolecular N—Hamine⋯Nthiazole hydrogen bond. The molecules are linked by hydrogen bonds and an S⋯O contact to form layers parallel to the bc plane.


Chemical context
Cyanoketene dithioacetals are versatile synthetic intermediates (Elgemeie et al., 2003a that have been utilized as building blocks for the synthesis of a wide range of heterocyclic compounds (Elgemeie et al., 2009(Elgemeie et al., , 2017a; they are also of general interest in pharmaceutical chemistry Elgemeie et al., 2016). Recently, we have described the synthesis of various antimetabolites starting from cyanoketene dithioacetals and related compounds, viz. cyanoketene S,S-acetals (Elgemeie, Mohamed, 2006), cyanoketene N,S-acetals (Elgemeie et al. 2017b), and cyanoketene N,N-acetals (Elgemeie et al., 2003b). As a part of this programme, the reaction of 2-(benzo[d]thiazol-2-yl)-3,3-bis(methylthio)acrylonitrile (1) with N-(2cyanoacetyl)-4-methylbenzenesulfonohydrazide (2) was investigated. The reaction between 1 and 2 in KOH-DMF gives an adduct for which four possible isomeric structures were considered (structures 3-6). Spectroscopic methods did not allow us to identify the product unambiguously and therefore the X-ray crystal structure was determined, confirming the exclusive presence of structure 6 in the solid state. The formation of 6 from the reaction of 1 and 2 is assumed to proceed via initial addition of the active methylene carbon atom of 2 to the double bond of 1, followed by elimination of CH 3 SH and cyclization via addition of the NH group to the cyano group of benzothiazole to give the favoured, kinetically and thermodynamically controlled product 6. The 1 H NMR spectra of the product revealed the presence of an amino group at = 8.84 p.p.m. and a pyridine methylthio group at = 2.45 p.p.m. in solution. Compound 6 and its derivatives showed interesting preclinical biological results and are currently being patented (Elgemeie et al., 2017c). ISSN 2056-9890

Structural commentary
The solid-state structure of 6 is shown in Fig. 1, the structure analysis thereby confirming the nature of the product. The molecule essentially consists of two planes; the toluenesulfonamide ring and the combined ring system involving the pyridone and benzothiazole rings. The former has a r.m.s. deviation of 0.04 Å and the latter of 0.01 Å (including all direct substituents), and the interplanar angle is 39.86 (4) . The pyridone and benzothiazyl rings are held coplanar by the intramolecular hydrogen bond N4-H03Á Á ÁN3 (Table 1). The contact N4-H02Á Á ÁN1 might also be classified as a hydrogen bond, with HÁ Á ÁN 2.24 (2) Å , but its angle is only 105.7 (15) . The nitrogen N4 is planar (angle sum 359.7 ) but N1 is pyramidalized (343.9 ).

Supramolecular features
The oyxgen atom of the dimethylformamide accepts two classical hydrogen bonds. The clearest packing feature is the formation of layers parallel to the bc plane ( Fig. 2), in which the hydrogen bonds H02Á Á ÁO99, H7Á Á ÁO3 ii and H97CÁ Á ÁN5 iv are involved (Table 1), together with the short contact S1Á Á ÁO3(x, 1 + y, z) 3.2662 (10) Å . The hydrogen bond H01Á Á ÁO99 i connects the layers in the third dimension.

Database survey
The 2-pyridone ring displays the usual features of a narrow angle at nitrogen and a wide angle at the carbonyl carbon (Table 2). A database search gave 555 hits (745 values) for the 2-pyridone ring, with average angles of 123.9 at nitrogen and 115.3 at C O. No other structures could be found in which a 2-pyridone ring is attached at the 5-position to the C2 atom of a thiazol ring.

Figure 1
The structure of the title compound in the crystal. Displacement ellipsoids represent 50% probability levels.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.20917 (