Novel environmentally benign procedures for the synthesis of styryl dyes

A series of styrylpyridinium, styrylquinolinium and styrylbenzothiazolium dyes have been synthesized by novel environmentally benign procedures. The condensation of 4-methylpyridinium methosulphate, 2- or 4-methylquinolinium methosulphate or 2-methylbenzothiazolium methosulphate with aromatic aldehydes was performed under solvent-free conditions or microwave irradiation in the presence of different basic or acidic reagents. The chemical structures of the derived styrylcyanine dyes were confirmed by 1H NMR and UV–vis spectroscopies and elemental analysis.