Novel environmentally benign procedures for the synthesis of styryl dyes

Abstract

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 1 H NMR and UVevis spectroscopies and elemental analysis.

Styryl dyes – synthesis and applications during the last 15 years

“…The condensation of 4‐methylpyridinium methosulphate, 2‐ or 4‐methylquinolinium methosulphate or 2‐methylbenzo‐thiazolium methosulphate ( 39 ) with aromatic aldehydes ( 40 ) was performed under solvent‐free conditions or microwave irradiation in the presence of different basic or acidic reagents. This new method gave excellent yields [29] (Scheme 12).…”

A novel general method for fast and easy preparation of cationic, neutral dimethinehemicyanine and dimethine dyes by uncatalysed Knoevenagel condensation

“…There are several microwave methods for the preparation of styryl dyes [21,22,32,33], but in all of them catalysts are used. This microwave approach is fast (2–8 min), green solvents, mixable with water, could be used (or other high‐boiling water‐soluble solvents) and produce generally high yields.…”

“…The classical synthesis of styryl dyes is often achieved through the reaction of 2‐ or 4‐methyl quaternary salts and aromatic aldehydes with catalyst at high temperature for a relatively long reaction time, which usually also results in the formation of undesired side products [1], low yields and considerable power consumption [20]. Recently, this group published a novel solvent‐free method for the preparation of styryl cationic dyes by microwave heating with different catalysts [21]. Microwave solvent‐free preparation of hemicyanine dyes by microwave heating with piperidine as the catalyst is also known [22].…”

“…The development of green chemistry and the search for new environmentally friendly synthetic methods are of general importance in organic chemistry, especially for the chemical industry. As mentioned, previous efforts have been devoted to develop a green procedure for the synthesis of styryl dyes [21]. To the best of our knowledge, there are no reports in the literature that refer to the use of 'green' solvents [25], such as glycerol [26], for the synthesis of cationic, dimethine and neutral styryl dyes by uncatalysed Knoevenagel condensation.…”

Novel styrylbenzothiazolium dye-based sensor for mercury, cyanide and hydroxide ions

“…A number of these styryl derivatives linked to crown ethers have been reported to exhibit high quantum efficiency fluorescence and selectivity for the metal ions [4,5]. However, these styryl dyes are widely used as sensitizers and other additives in the photographic industry [6]. Several potential applications, such as artificial photosynthesis [7], http photocatalysis [8], molecular photovoltaic cells [9], molecular informatics [10], and optoelectronic devices [11], are beginning to emerge from this new field of research.…”