Synthesis and Characterization of Some New Azo Dyes Derivatives Via Chalcone and Study Some of Their Biological Activity

This work includes synthesis of new six membered heterocyclic rings with effective amino group using the reaction of benzylideneacetophenone (chalcone) (1) with thiourea or urea in alcoholic basic medium to form: 1,3-thiazen-2-amine (2), and 1,3-oxazin-2-amine (8) respectively. The diazotization reaction was carried out with sodium nitrite in presence of hydrochloric acid to form diazonium salts which suffered coupling reaction with naphthols and phenols in the presence of sodium hydroxide to form colored azo dyes (4-7, and 10-13). o-methylation reaction of compounds (7) and (10) yielded : 1,3-thiazin -2-yldiazenyl (14), and 1,3-oxazin-2-yl-diazenyl (15) respectively. The new compounds were characterized using various physical techniques like: UVVis., FT-IR, and 1 HNMR spectra. Some new compounds were tested against bacteria.


Introduction:
Chalcone is an α,β-unsaturated ketone , produced from aldol condensation reaction of acetophenone with benzaldehyde or substituted benzaldehyde in presence of sodium hydroxide as a catalyst as shown below [1-4]: Its general formula C 6 H 5 CH=CHCOPh has two isomers cis and trans , trans isomer is more common [1,3].It has several names such as : benzylideneacetophenone , benzalacetone , and methyl styryl ketone [5]., The name "Chalcone" was given by Kostanecki and Tambor; Chalcones are well known intermediates for synthesizing various heterocyclic compounds [3,4].Chalcones can be isolated from several plants, and are precursors of flavones compounds, they are similar to enamines, they contain a double bond and prepared from intervention condensation reaction with urea or thiourea and other organic nitrogen compounds to form heterocyclic compounds [3], the reaction should carried out with strong basic conditions and low temperatures to Open Access yield compounds used in pharmaceutical and an industrial purposes [1,6].When a primary aromatic amine is treated with nitrous acid at low temperature, it will converted to a diazonium salt, the simplest form is benzenediazonium chloride [7,8].Coupling reaction of azo dye is an organic electrophilic substitution reaction between a diazonium salts and other aromatic compound [8], the products will absorb longer wavelengths of light especially in the visible region compared with the reactants because of the conjugation ,therefore, aromatic azo dyes tend to be brightly colored due to the extended conjugated system [8,9].Also products of azo coupling reaction used to form pharmaceutical drugs such as sulfa drugs [10,11].
The different application fields of synthetic azo compounds are widely such as foods, medicines, cosmetics, paints, shipbuilding, automobile, plastics,industry,cable manufacture, etc. [12,13].However, the traditional application field of the synthetic azo dyes still remains the textile industry, and the finishing of fibrous materials in order to impart simultaneously with coloration [6,13].Using gold (Au) nanoparticles supported on TiO 2 as a catalyst in the the aerobic oxidation of aromatic anilines to aromatic azo compounds, also using Au as a hydrogenation catalyst on TiO 2 making it possible to prepare azo compounds directly from nitro aromatics through a two-step (hydrogenation followed by aerobic oxidation), one-pot, and one-catalyst reaction.In addition, the catalytic process is efficient for the synthesis of symmetric and a range of asymmetric aromatic azo compounds from the mixtures of two anilines substituted with electron-donor and electronacceptor constituents [14].
The aim of this work is to prepare and characterize new series of azo compounds starting from α, βunsaturated ketone which it were expected to have a biological activity.

Results and Discussion:
The compounds (2) and (8) were prepared using the reaction between benzylideneacetophenone (chalcone) (1) and thiourea or urea in presence of sodium hydroxide solution (40%) as shown in scheme -1: H H
H H