Thiazoline and thiazoloxazole in synthesis of novel meso-substituted mono-, tri-, and hepta-methine cyanine dyes

Abstract

2-Cyanomethylene (2-ethoxy carbonylmethylene)-4,5-dihydrothiazolin-4-one 1a,b and 2-cyanomethylene (2-ethoxy carbonylmethylene)-4,5-dihydrothiazolo [3,2-a]oxazole 3a, b were synthesized as starting material. Reaction of both compounds 2a, b and 3a, b with N-methylheterocyclic quaternary salts afforded meso-substituted monomethine cyanine dyes 4a– d and 9a– d, respectively. Reaction of compounds 1a, b and 8a, b with ethyl orthoformate gave the intermediate compounds 5a, b and 10a, b, followed by the reaction with 1,2-dimethyl quinolinium iodide resulted in meso-substituted trimethine cyanine dyes 6a, b and 11a, b, respectively. Also, reaction of both 2a, b and 3a, b with 2-chlorocyclohexane-1,3-dicarboxaldehyde followed by the reaction with 1,2-dimethyl quinolinium iodide afforded the asymmetrical heptamethine dyes 8a, b and 13a, b. The new compounds were characterized by elemental analysis, visible absorption, 1H NMR, IR Spectroscopy and Ms spectral data. Relation between the constitution and the UV/Vis spectroscopic properties of these dyes has been studied.