N(OC(C)(C)C)=O.[Br:8][C:9]1[CH:15]=[CH:14][C:12](N)=[C:11]([CH3:16])[C:10]=1[CH3:17].[CH3:18][S:19]SC>[Cu]>[CH3:17][C:10]1[C:11]([CH3:16])=[C:12]([S:19][CH3:18])[CH:14]=[CH:15][C:9]=1[Br:8]603 g (5.85 mol) of tert-butyl nitrite and 375 g of copper powder (5.9 mol) are initially charged in 3000 ml of dimethyl disulfide, and 761 g (3.75 mol) of 4-bromo-2,3-dimethylaniline are added dropwise at 50-58° C. The mixture is then stirred at 75-80° C. for 9 hours. For work-up, the mixture is cooled, the residue is filtered off and the filtrate is washed with saturated aqueous NaHCO3 solution. For purification of the product, the organic phase is separated by distillation. Initially, excess dimethyl disulfide is removed under atmospheric pressure. 1870 g of dimethyl disulfide (purity >97% according to GC) are recovered. The residue is then subjected to fractional distillation under reduced pressure (0.1 mbar).
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