S=[C:2]1[NH:6][C:5]2[CH:7]=[C:8]([C:11]#[N:12])[CH:9]=[CH:10][C:4]=2[O:3]1.S(Cl)([Cl:15])=O>CN(C=O)C.C(Cl)Cl>[Cl:15][C:2]1[O:3][C:4]2[CH:10]=[CH:9][C:8]([C:11]#[N:12])=[CH:7][C:5]=2[N:6]=1To a mixture of 2-thioxo-2,3-dihydrobenzooxazole-5-carbonitrile (2.56 g, 14.5 mmol) and thionylchloride (14.1 mL) was added two drops of DMF. The mixture was heated at 65-70° C. for 1 h. Then the mixture was cooled to rt and diluted with CH2Cl2. The solvent and excess thionylchloride were removed under reduced pressure. The residue was purified by column chromatography on silica gel (eluent: 20% EtOAc in Petroleum ether) to give 2-chlorobenzooxazole-5-carbonitrile 1.69 g (65%).
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