Synthesis
General procedure for the synthesis of 5-nitrobenzothiazole from dimethylthiocarbamide and 2,4-dinitrochlorobenzene: 1-chloro-2,4-dinitrobenzene (8 g, 39 mmol) was mixed with N,N-dimethylthiocarbamide (14.5 ml, 178 mmol) and heated to react for 3 hr at 60 °C, during which a yellow precipitate was produced. Subsequently, xylene (20 ml) was added to the reaction mixture and the mixture was heated to reflux for 4 hours, after which stirring was continued for 18 hours at room temperature. After completion of the reaction, the mixture was diluted with ethanol (12 ml), filtered and the solid was washed with minimum amount of ethanol. The brown solid obtained was dissolved in ethanol (100 ml), heated to boiling and thermally filtered. The filtrate was concentrated to about 80 ml and left at room temperature overnight. Finally, the precipitated solid was collected by filtration and washed with ethanol to give 1.9 g (32% yield) of 5-nitro-1,3-benzothiazole. The structure of the product was confirmed by 1H NMR (CDCl3): δ 8.11 (1H, d, J=8.6 Hz), 8.36 (1H, dd, J=2.2, 8.8 Hz), 9.01 (1H, d, J=2.0 Hz), 9.20 (1H, s).
References
[1] Patent: WO2005/28445, 2005, A2. Location in patent: Page/Page column 27-28
[2] Patent: US2001/345, 2001, A1
