TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The cyclization reaction is carried out in presence of alkali promoter. The reaction of (III) with halopropane is performed in presence of an acid binding agent. The condensation reaction is performed in presence of condensing agent and alkali promoter in a solvent. Preferred Components: The sulfur containing cyclizing agent is carbon disulfide, potassium isothiocyanate, isothiocyanic acid, isothiocyanate, thiophosgene, thiourea or substituted thiourea. The halopropane is chloropropane, bromopropane or iodopropane. The alkali promoter in cyclization reaction i.e. sodium, sodium hydride, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, potassium carbonate, potassium hydroxide, sodium hydroxide, triethylamine, pyridine, 2,6-dimethylpyridine, 4-dimethylaminopyridine, N-methylmorpholine, N-ethylmorpholine, diisopropylethylamine, 1,5-diaza-bicyclo(4.3.0)-non-5-ene, 1,8-diazabicyclo(5.4.0)-undec-7-ene or 1,4-diazabicyclo(2.2.2)octane. The acid binding agent is potassium carbonate, potassium tert-butoxide, potassium hydroxide, sodium hydroxide, sodium methoxide, sodium ethoxide, triethylamine and pyridine. The condensing agent is N,N'-dicyclohexylcarbodiimide, carbonyldiimidazole, N,N'-diisopropylcarbodiimide, 1-hydroxybenzotriazole, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate, O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, 2-(1H-benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate or benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate. The alkali promoter in condensation reaction is triethylamine, pyridine, 2,6-dimethylpyridine, 4-dimethylaminopyridine, N-methylmorpholine, N-ethylmorpholine, diisopropylethylamine, 1,5-diaza-bicyclo(4.3.0)-non-5-ene, 1,8-diazabicyclo(5.4.0)-undec-7-ene or 1,4-diazabicyclo(2.2.2)octane. The condensation reaction solvent is toluene, xylene, ethyl acetate, isopropyl acetate, butyl acetate, chloroform, dimethyl sulfoxide, N,N-dimethylformamide or acetonitrile.