4, prime ,5 prime :5,6.

2-Amino-3-methyl-1-oxo-1HAH-pyridol left bracket 1,2-a right bracket benzimidazole-4-carbonitrile(4), the key compound in the synthesis of oxazolo left bracket 4 prime ,5 prime :5,6 right bracket pyrido left bracket 1,2-a right bracket benzimidazole derivatives, was prepared by reduction of the azo dye obtained from phenyldiazonium-4-sulfonic acid salt coupled with 3-methyl-1-oxo-1H5H-pyrido left bracket 1,2-a right bracket benzimidazole-4-carbonitrile. The condensation of (4) with acetic anhydride yielded 2,4-dimethyloxazolo left bracket 4 prime ,5 prime :5,6 right bracket pyrido left bracket 1,2-a)benzimidazole-5-carbonitrile (5) and condensation of (4) with ethyl benzoate and ethyl 4-methoxybenzoate in PPA afforded the corresponding 2-aryl-4-methyloxazolo left bracket 4 prime ,5 prime :5,6 left bracket pyrido left bracket 1,2-a right bracket benzimidazole-5-carbonitrile (7a-7b). Bis-1,2- left brace 4-methyl oxazolo- left bracket 4 prime ,5 prime :5,6 left bracket pyrido left bracket 1,2-a right bracket benzimidazol left bracket 2 left bracket yl left bracket 5 left bracket carbonitrile right brace ethylene (9a) and bis-1,4- left brace 4-methyl oxazolo-4 varies directly as ,5 prime :5,6 left bracket pyrido left bracket 1,2-a right bracket benzimidazol-2-yl-5-carbonitrile right brace benzene (9b) were similarly obtained by condensation of two moles of (4) with 1 mole of fumaric acid and diethyl terephthalate, respectively in PPA and phosphorus oxychloride. The fluorescence properties of the compounds (5) 7a-7b and 9a-9b were studied. Some of the compounds were evaluated as fluorescent whitening agents for polyester fibers.