engleski

PALLADIUM CATALYZED SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF NOVEL 2- ARLYBENZOXAZOLE DERIVATIVES

Benzoxazole scaffold is a core structure in many synthetic compounds having different biological activities such as anti-inflammatory, anticancer and antimicrobial [1]. In the search for more efficient drugs, transition metal- catalyzed cross-coupling reactions that enable carbon–carbon bond construction, such as Sonogashira reaction, emerged as an attractive solution to synthesizing challenges, which has found widespread use in the synthesis of benzoxazole derivaties substituted with alkynyl fragments.[2] From the viewpoint of green chemistry, DESs (Deep eutectic solvents) are attractive since some of them have proven to be biodegradable and compatible with enzymes further increasing their interest [3]. In this work we present synthesis of 2-(3-alkynly- 4-O-alkylphenyl)benzoxazoles by Sonogashira reaction. 4-O-alkylated benzaldehyde derivatives for the synthesis of target benzoxazole derivatives were prepared by alkylation reaction of 4-hydroxybenzaldehyde in DES (ChCl/glycerol) which were then converted in Schiff bases by mechanochemical reaction with 2-aminophenole. Microwave assisted cyclization of Shiff bases gave 2- arylbenzoxazoles. Introduction of alkynyl substituents at position 3 of phenyl ring was performed by Pdcatalyzed Sonogashira cross-coupling reaction. Structures of all newly prepared 2-(3-alkynly4-O- alkylphenyl)benzoxazoles were confirmed by 1H and 13C NMR spectroscopy.

benzoxazole, deep eutectic solvent, microwave reaction, Sonogashira reaction

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