By reaction of 10-(3-chloropropionyl)-2-(ethoxycarbonylamino)phenothiazine (I) with diethylamine in refluxing toluene.
This compound can be obtained in two different ways: 1) The bromination of 1-(2-ethylindan-2-yl)-1-ethanone (I) with Br2 in ether gives 2-bromo-1-(2-ethylindan-2-yl)-1-ethanone (II), which is then cyclized with formamide by heating at 170-80 C. 2) The cyclization of alpha,alpha'-dibromo-o-xylene (III) with 4-penten-2-one (IV) by means of tetrabutylammonium hydroxide in toluene at 100 C gives 1-(2-vinylindan-2-yl)-1-ethanone (V), which is brominated with Br2 in dichloromethane to yield 2-bromo-1-(2-vinylindan-2-yl)-1-ethanone (VI). The cyclization of (VI) with formamide at 160 C as before affords 4-(2-vinylindan-2-yl)-1H-imidazole (VII), which is finally hydrogenated with H2 over Pd/C in ethanol.