The absorption spectra of aqueous solutions of monochIorotriazine reactive dyes, C.I. Reactive Red 9 and Reactive Orange 13 were measured in the presence of 5, 10, 25 and 50% (v/v) of ethanol, pyridine and dioxane-water mixtures and in varied concentrations of KCI, NaCl and LiCl. The varying position, intensity and shape of absorption bands are interpreted in terms of aggregation and disaggregation of dyes in solutions. The aggregation behaviour of the reactive dyes in solutions and in the presence of additives is related to their apparent deviations from Beer's law and aggregation numbers (N). The aggregation constant (K) of the rnonomer/dimer equilibrium is calculated..Dyes in ethanol-water mixtures record a larger aggregation number and aggregation constant than in the presence of pyridine. Dioxane is classified as a non-polar solvent and hence has a more disaggregating influence. The value of the aggregation number and constant are increased with increasing salt conentration and the order of degree of aggregation is KCl > NaCl > LiCl related to the order of ionic radii of K\ Na" and Li" ions. 507

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Condensed heterocyclic systems containing N-& S-medium-sized rings, in particular, thiazepine, thiazocine, and thiazonine systems are important substructures present in a large variety of biologically active natural products. Methods for the formation of thiazonines and higher ring systems, however, remain largely unknown. The research presented addresses the synthesis and characterization of new heterocyclic skeletons incorporating N-& S-medium-sized-rings fused to quinolines to form the targeted tetracyclic 1,4-thiazocines, 1,4-thiazonines and 1,4-thiazecines by Friedel-Crafts cycliacylation and Beckmann-rearrangement sequences. The ambient conditions, short-reaction times and easy work-up procedures make this synthetic strategy a better protocol for the synthesis of medium-sized heterocyclic rings bearing nitrogen and sulphur atoms.

An efficient methodology for the synthesis of novel substituted pyrido[3,2,1-jk]carbazole via Friedel-Crafts cyclialkylations is reported. The methodology was realized by three-step protocol involved the addition of carbazole to 3-methylcrotononitrile. The resulted nitrile was hydrolyzed to desired ester, followed by addition of Grignard reagents to afford tertiary alcohols and/or reacted directly with different Grignard reagent to form the desired ketones. The later ketones were converted to both secondary and tertiary alcohols by reduction with LAH and addition of Grignard reagents respectively. These carbinols were cyclialkylated under Friedel-Crafts conditions catalyzed by AlCl3/CH3NO2, PTSA and PPA to give tri-and tetrasubstituted pyrido[3,2,1-jk]carbazole

A new synthetic approach for the synthesis of novel 5H-dibenz [2,3-c]azocine derivatives is reported. The key step of this methodology is based on Friedel-Crafts ring closure of nitrogen containing carboxylic acids and alkanols in the presence of AlCl 3 , P 2 O 5 or PPA catalysts in overall high yields. The starting carboxylic acids were prepared via an unequivocal synthetic pathway by the basic hydrolysis of trimethyloxindole followed by N-arylation reactions.