Ethyl 2-(tert-butoxycarbonylamino)-1,3-benzothiazole-6-carboxylate

In the crystal of the title compound, C15H18N2O4S, inversion dimers are formed by intermolecular N—H⋯N hydrogen bonds and weak C—H⋯O contacts. These dimers stack up along [100] through inversion-related π–π interactions between thiazole rings [centroid–centroid distance = 3.790 (2) Å] and the thiazole and benzene rings [centroid–centroid distance = 3.845 (2) Å] and C—H⋯π contacts.

The molecular structure of the compound is shown in Fig. 1. The benzothiazole moiety in this structure is very similar to other benzothiazole compounds reported before (Lynch, 2002;Matković-Čalogović et al., 2003). The dihedral angle between the carbonylamino group and the planar central 9-membered ring system is 7.59 (6) °, and between the central rings and the ethylcarboxylate group is 7.72 (6) °, respectively.

Experimental
Di-tert-butyl dicarbonate (4.92 g, 22.5 mmol) and 4-dimethylamino pyridine (2.06 g, 16.9 mmol) were added to a solution of ethyl 2-aminebenzothiazole-6-carboxylate (the starting compound) (2.5 g, 11.3 mmol) in dry THF (300 ml), and stirred for 22 hours at room temperature. Then the solvent THF was evaporated, and the residue was extracted with 1 liter of dichloromethane. The dichloromethane washed with 1 N aq HCl, water, and brine, sequentially, and dried with Na 2 SO 4 .
Further filtration and concentration yielded the dried compound as a yellow solid [2.61 g, yield: 72%]. The solid was dissolved in DMF and filtered. The DMF was evaporated slowly at room temperature for a week, giving colorless needle crystals.

Refinement
All H atoms bound to C and N atoms were refined as riding, with C-H distances in the range of 0.93 to 0.97 Å and N-H distances of 0.86 Å, with U iso (H) = 1.2U eq (C, N); 1.5U eq (C methyl ). Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are shown at the 50% probability level. Hydrogen atoms are shown as spheres of arbitrary radii.

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.
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 > σ(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.