4-Bromobenzohydrazide → 2-(4-Bromophenyl)-5-methyl-1,3,4-oxadiazole

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4-Bromo-benzoic acid hydrazide (12.90 g, 60 mmol) and N,N-dimethylacetamide dimethyl acetal (12 mL, 82.0 mmol) were dissolved in N,N-dimethylformamide (100 mL) and the solution heated to 60° C. for 2 hours. The solution was concentrated in vacuo and the residue taken up in toluene (80 mL) and treated with para-toluenesulfonic acid monohydrate (200 mg, 1.50 mmol). The mixture was heated to reflux for 2 hours, allowed to cool, and the product crystallised from the solution and was collected by filtration. The crude product was washed with ether and dried in vacuo to yield a white solid. The filtrate was concentrated in vacuo and the residue combined with the white solid, dissolved in toluene (50 mL) and treated with para-toluenesulfonic acid monohydrate (100 mg, 0.75 mmol). The mixture was heated to reflux for 3 hours, allowed to cool and concentrated in vacuo. The residue was purified by column chromatography on silica gel eluting with pentane:ethyl acetate 80:20 to 40:60 to yield the title product, 12.00 g.

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