Reaction Steps
The amino precursors of ABQ-38 and ABQ-95, (E)-7-ethyl-2-(5-amino-2-chlorostyryl)benzimidazole IIv and (E)-5-methyl-2-(5-amino-2,4-dichlorostyryl)benzothiazole IId, respectively, were prepared by the reduction of the corresponding nitro derivatives with hydrazine in the presence of nickel boride in dry methanol, see FIG. 3. (E)-7-ethyl-2-(5-amino-2-chlorostyryl)benzimidazole IIv was photocyclized as described (BQS Method 1) to give 3-amino-7-ethylbenzimidazo[3,2-a]quinolinium chloride (ABQ-38) as a yellow solid: 1H NMR (500.13 MHz, DMSO-d6): δ ppm 9.05 (d, 1H, J=8.50 Hz), 8.88 (d, 1H, J=9.0 Hz), 8.56 (d, 1H, J=9.5 Hz, 8.27 (d, 1H, J=8.5 Hz), 8.23 (d, 1H, J=9.50 Hz), 7.90 (t, 1H, J=7.5 Hz), 7.81 (t, 1H, J=7.5 Hz), 7.43 (dd, 1H, J=8.5, 2.5), 7.27 (d, 1H, J=2.5 Hz), 4.83 (q, 2H, J=7.0 Hz), 1.48 (t, 3H, J=7.0 Hz); UV-vis (95% EtOH) λmax/nm (e): 409 (1410), 351 (8104), 336 (9815) and 271 (20866); HRMS calcd for C17H16N3 (compound without the chloride counter ion) 262.1, found by ESI at m/z 261.9. (E)-5-methyl-2-(5-amino-2,4-dichlorostyryl)benzothiazole IId was photocyclized as described (BQS Method 1) to give 3-amino-2-chloro-10-methylbenzothiazolo[3,2-a]quinolinium chloride (ABQ-95) as a yellow solid: 1H NMR (500.13 MHz, DMSO-d6): δ ppm 9.17 (s, 1H), 8.92 (s, 1H), 8.63(AB quartet, 2H, J=9.5 Hz), 8.48 (d, 1H, J=8.5 Hz), 7.76 (d, 1H, J=8.5 Hz), 7.53 (s, 1H), 6.50 (m, 2H), 2.70 (s, 3H); UV-vis (95% EtOH) λmax/nm (e): 429 (4417), 380 (10 387), 282 (22 568) and 214(2650); HRMS calcd for C16H12ClN2S 299.0 (without the chloride counter ion), found by ESI at m/z 299.0 M+.
