Aza-benzazolium containing cyanine dyes

Patent Aza-Benzazolium Containing Cyanine Dyes R.P. Haugland etal, 

Equimolar amounts of 2-methylthiooxazolpyridine and methyl tosylate were heated together at 100-110°C 1 hour (1) and the product isolated and used directly without purification in step 2. 

4-Methyl-2-((l-methyl-2-N,N-diethylmethyleneamine-4-(methylene-2-(4-aza-benzoxazolium tosylate))-dibydroquinoline iodide (cyanine dye intermediate) 

To 10 ml THE was added 4-bromobenzyldiethylamine, the mixture cooled to —78°C, 0.8 ml 2.5 M n-BuLi added, followed by 0.173 g 1,4-dimethyl-2-quinolone dissolved in 10 ml THE. After one hour, 1 ml HO Ac and the product from Step 1 (0.67 g) were added followed by 1 ml TEA. At ambient temperature the volatiles were evaporated and 7 ml methyl alcohol, 2.25 g Nal, and NaOH (0.8 g in 50 ml) added. 

The product was isolated and re-crystallized from a mixture of DME and EtOAc. 

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Haugland, R. P. Yue, S. T. Aza-benzazolium-containing cyanine dyes and their use in fluorescent biological stains. PCT Int. Appl. WO 2000066664, 2000. 

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