[OH:1][C:2]1[C:11]([N+:12]([O-])=O)=[CH:10][CH:9]=[C:4]([C:5]([O:7][CH3:8])=[O:6])[C:3]=1[C:15]([O:17][CH3:18])=[O:16].[C:19](=S)(OCC)[S-:20].[K+]>[C].[Pd].C(OCC)(=O)C>[CH3:8][O:7][C:5]([C:4]1[CH:9]=[CH:10][C:11]2[N:12]=[C:19]([SH:20])[O:1][C:2]=2[C:3]=1[C:15]([O:17][CH3:18])=[O:16])=[O:6]A 10% palladium carbon catalyst (2.5 g) was added to a solution of the nitro compound mixture (4.3 g, 16.8 mmol) in ethyl acetate (60 ml) and stirred under hydrogen atmosphere at room temperature for 3 hours. The reaction solution was filtered off through celite and the filtrate was concentrated. The residue was dissolved in methanol (50 ml), potassium O-ethyl dithiocarbonate (1.76 g, 11.0 mmol) was added thereto and the mixture was heated to reflux for 16 hours. After cooling, the solvent was evaporated in vacuo. The residue was diluted and acidified with 2N hydrochloric acid and extracted with ethyl acetate. The organic layer was washed with water and a saturated sodium chloride solution successively and dried over anhydrous magnesium sulfate and the solvent was evaporated therefrom. The residue was crystallized from ether to provide 1.61 g (yield 60%) of 6,7-bis(methoxycarbonyl)-2-mercaptobenzooxazole as yellow crystals.
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