For the synthesis of novel thiazolo[3,2-a]benzimidazol-3-ones and thiazolo[3,2-a]benzimidazoles, two methods have been developed which afforded the target compounds in relatively good yields by a pot process. The reaction between 2-mercapto-1H-benzimidazoles, acetophenone derivatives and 4-methylcyclohexanone in acid medium gave the tricyclic and tetracyclic benzimidazole compounds. We have also studied the flexibility of the position-7 of the thiazolobenzimidazoles by introducing the nitro and the methyl group. All compounds were characterized by means of
Five symmetrical near infrared dyes having different linker between the two heterocycles were synthesized by condensation of N-alkylbenzo[c,d]indolium salts with either squaric acid or imine. All synthesized dyes showed strong absorbance in the near-infrared region of 850-1015 nm and can be used as nucleic acid detection or fluorescent labeling agents for proteins. Three of the dyes 21, 22 and 25 containing functionalized N-substituents (ester group) can be further modified or covalently attached to target. The structures of these cyanine dyes where characterized by virtue of NMR, UV, MALDI and Elemental analysis.
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