South African Journal of Chemistry
On-line version ISSN 1996-840X
Print version ISSN 0379-4350
RAJESHA, G.; KIRAN KUMAR, H.C.; BHOJYA NAIK, H.S. and MAHADEVAN, K.M.. Synthesis of new benzocoumaryl oxadiazolyls as strong blue-green fluorescent brighteners. S.Afr.j.chem. (Online) [online]. 2011, vol.64, pp.88-94. ISSN 1996-840X.
The benzocoumarin-3-ethylcarboxylate 2 on treatment with hydrazine hydrate at room temperature afforded benzo-coumarin-3-carbohydrazide 3. The compound 3 served as key intermediate in the synthesis of the title compounds. Thus, benzocoumarin-1,3,4-oxadiazolyls 6a-e were obtained in two ways, i.e. one by direct cyclization of benzocoumarin-3-carbohydrazide 3 with substituted benzoic acids in POCl3 and the other by cyclization of Schiff bases of compounds 5a-e in the presence of bromine/acetic acid. The structures of the novel benzocoumaryl oxadiazolyls 6a-e were confirmed by spectral analysis. The benzocoumarin-1,3,4-oxadiazolyls 6a-e exhibited strong blue and green fluorescent properties. The Stoke's shifts range from 43 to 165 nm. The absorption and fluorescence maxima of the benzocoumaryl oxadiazolyls showed good bathochromic shifts.
Keywords : Benzocoumarin-3-ethylcarboxylate; benzocoumaryl oxadiazolyls; fluorescent brighteners.