The use of oxonium salts in the synthesis of mono-, β-substituted dimethine and styryl cyanine dyes

Pyrazolopyrylium perchlorate salt derivatives were obtained from the reaction of 5-chloro-4-formyl-1-phenyl pyrazole with phenylpyrazolone, [4(2-propenyl)-1,6-ene-2-cyclohexanone] and cyclohexanone give pyrazolopyrylium perchlorate salt derivatives. Reaction of the latter compounds with 2(4)-methyl substituted heterocyclic quaternary salts gave the pyrazolopyrylium 4[2(4)]-monomethine cyanine dyes. Meanwhile, reaction with amide compounds gives an intermediate compounds which when reacted with 2(4)-methyl substituted heterocyclic quaternary salts gave the pyrazolopyrylium 4[2(4)]-β-substituted dimethine. Reaction of the intermediate compounds with various aromatic aldehydes followed by the reaction with 2-methyl quinolinium ethiodide salt give bis styryl cyanine dyes. Elemental analyses, visible absorption, IR, 1H NMR spectroscopy and mass spectra established the structures of these compounds. The relationship between the structure and properties of these dyes is discussed.