S. Seshadri

Synthesis of benzimidazo-[1,2-a]-quinolines: fluorescent disperse dyes

Abstract The paper describes the synthesis of 7-diethylaminobenzimidazo-[1,2-a]-quinoline-3-carbonitrile (a highly fluorescent yellow compound) and its reduction to the formyl derivative. Styryl derivatives of the formyl compound gave attractive orange to pink-red dyeings on polyester. Oxidative cyanation of benzimidazo-[1,2-a]-quinoline-3-carbonitrile gave the red dinitrile. Absorption-emission spectra of the synthesised dyes were recorded.

Azo disperse dyes derived from 3-amino-7-nitro-2H-1,2-benzothiazine 1,1-dioxide

Abstract 3-Amino-7-nitro-2H-1,2-benzothiazine 1,1-dioxide was utilised to prepare a range of azo disperse dyes for polyester. These dyes were subjected to methylation, bromination and cyanation reactions and the resultant derivatives were studied with respect to colour-constitution relationships. Application properties of the dyes on polyester and their fastness properties were evaluated. The dyes were characterised by IR, PMR and visible absorption spectra.

Absorption-emission spectra studies of 3-hetarylcoumarins

Abstract The synthesis of several coumarins substituted with a five-membered heterocyclic ring at the 3-position have been synthesised. The hetaryl rings substituted at the 3-position are the furyl, oxazolyl and the oxadiazolyl systems. The 3-furylcoumarins were prepared by reacting salicylaldehyde derivatives with a furylacetonitrile derivative. The oxazolyl and the oxadiazolyl derivatives were synthesised from coumarin-3-carboxylic acid derivatives by the usual routes. The absorption characteristics of these compounds have been recorded.

Synthesis of Fluorescent 2,3-Fused Coumarin Derivatives

Abstract 7-Diethylamino-3-substituted coumarin-2-imine derivatives are utilised in the synthesis of a new range of fluorescent coumarin derivatives. The coumarin derivatives were applied to polyester and their properties evaluated. Visible absorption-emission characteristics of the compounds were studied.

Synthesis of 1,2-fused benzimidazo heterocycles from benzimidazole-2-acetonitrile and heterocyclic ortho-chloroaldehydes

Abstract The condensation of 5-chloro-4-formyl-3-methyl-1-phenylpyrazole with benzimidazole-2-acetonitrile led to the formation of the fused heterocycle 3-methyl-1-phenyl-1H-pyrazolo [4,3:5,6]pyrido[1,2-a]benzimidazole-5-car-bonitrile. Similar condensation of 2-chloro-3-formylquinoline derivatives gave the corresponding 1,2-fused benzimidazo heterocycles. These heterocycles underwent oxidative cyanation.

Synthesis of 3-hetarylcoumarins from 3-acetylcoumarins

Abstract Vilsmeier reaction (DMF/POCl3) on the phenylhydrazones and semicarbazones of 3-acetylcoumarin derivatives led to a simple synthesis of 3-(4-formylpyrazol-3-yl)coumarins. Fischer indole reaction on the phenylhydrazones of 3-acetylcoumarins gave rise to 3-indolylcoumarins. The resulting pyrazolyl and indolylcoumarins were studied for their absorption-emission characteristics and they have been evaluated on polyester.

Synthesis of 1,1-dicyano-2,4-diaryl-1,3-butadienes—a novel chromophore

Abstract A series of bright, attractive disperse dyes have been obtained by the condensation of acetophenone with malononitrile and reacting the resultant vinylogous reactive methyl compound with aldehydes. The resultant 1,1-dicyano-2,4-diarylbutadienes are bright strong colours with good dyeing properties on polyester. In one case the above product was submitted to oxidative cyanation to yield a novel chromophore, namely the tricyanobutadiene derivative, which has a deeper colour and improved dyeing properties.

Studies in the vilsmeier-haack reaction: part XXV—synthesis of 3-hetarylcoumarins by the application of the vilsmeier-haack reaction

Abstract Coumarin-3-acetic acid derivatives have been utilised in the Vilsmeier formylation reaction and the products thus obtained have been converted into 3-hetarylcoumarins, the absorption and emission characteristics of some of which are reported.

Synthesis of new fluorescent dyes from 6-methoxy-1-chloro-3,4-dihydronaphthalene-2-carboxaldehyde

Abstract The synthetic utility of the Vilsmeier reagent to generate new precursors for condensed heterocycles has been extended to the synthesis of some new fluorescent compounds. 6-Methoxy-1-chloro-3,4-dihydronaphthalene-2-carboxaldehyde was used to synthesise new benzimidazo-[1,2-a]-quinolines, quinazolines, thienylbenzimidazole, benzo-[h]-quinolines, benz-[g]-indazoles and isothiazole derivatives. The efficacy of the aldehyde derivative was further extended to synthesise strongly fluorescent pyrano, iminothiopyrano and exocyclic dicyano derivatives. The compounds were characterised by IR, 1H-NMR and visible absorption-emission spectra; they were also applied to polyester as fluorescent dyes and their properties evaluated.

Azo acid dyes derived from 3-ammo-7-nitro-2H- 1,2-benzothiazine-1,1-dioxide

Abstract A series of azo acid dyes for wool were prepared from 3-amino-7-nitro-2H-1,2-benzothiazine-1,1-dioxide. These dyes were subjected to chroming on the fibre and their colour and fastness properties assessed. Red to black dyeings of good fastness properties were obtained.