[CH3:1][C:2]1[S:3][C:4]2[CH:10]=[C:9]([CH3:11])[CH:8]=[CH:7][C:5]=2[N:6]=1.[Br:12][CH2:13][CH2:14][OH:15]>C(OCC)(=O)C>[Br-:12].[OH:15][CH2:14][CH2:13][N+:6]1[C:5]2[CH:7]=[CH:8][C:9]([CH3:11])=[CH:10][C:4]=2[S:3][C:2]=1[CH3:1]A solution of 2,6-dimethylbenzothiazole (13.0 g) and 2-bromoethanol (100 g) was stirred and heated in an oil bath to 120° C. for 96 hours. After cooling the reaction mixture to room temperature, adding ethyl acetate (150 ml) and stirring for 1 hour, the resultant solid was filtered and collected. The solid was then dissolved in methanol (150 ml) and charcoal (2 g) was added. The charcoal was removed by passing through a pad of Celite. The solution was then concentrated to a small volume and triturated with acetone (200 ml). The solid was collected, washed with acetone (2×30 ml), ethyl acetate (2×30 ml) and dried in an oven under high vacuum at 50 C. overnight to obtain 13.95 g (61%) of 4b.
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