Synthesis and identification of some new n-substituted quinazoline-4-one, thiazine-4-one and tetrazoline rings incorporating n-ethyl-2-(Benzylthio)benzimidazole acetate and study their application as anti-oxidant agent

A new series of 2-Mercaptobenzimidazole derivatives were synthesized. Quinazoline-4-one, thiazine-4-one and Tetrazoline derivatives. These compounds can be prepared by alkylation of 2-Mercaptobenzimidazole [2-MBI] with benzyl chloride in basic medium to produce 2- benzyl thiobenzimidazole [1], then the compound [1] was mixed with sodium hydride in dioxane at (0-5C0) to give the salt of compound [1]. Then the salt was reacted with ethyl chloro acetate to yield ethyl 2-(benzylthio) benzimidazole acetate compound [2] as a starting compound [2]. Thereafter, compound [2] was treated with hydrazine hydrate to afford N-acetohydrazide-2-(benzyl thio) benzimidazole [3] then reacted with a different substitution aromatic aldehyde in absolute ethanol to give Schiff’s bases derivatives [4-10]. The reactions of compounds [4-10] were carried out through three pathways for cyclization: The first pathway involved a reaction with 2- amino benzoic acid to afford Quinazoline-4-one derivatives [11-17]. The second pathway consists of reaction with 2-marcaptobenzoic acid to produce thiazine-4-one derivatives [18-24]. The third pathway involved reaction with sodium azide to obtain tetrazoline derivatives [25-31]. The new prepared compounds were identified by [FTIR, 1H-NMR and 13C-NMR] and their physical properties were measured. Furthermore, we have evaluated of anti-oxidant activities in-vitro of the new synthesized compounds were tested with DPPH radical cation decolorization assays.