CN(C=O)C.C[O-].[K+].[N+:9]([C:12]1[CH:17]=[CH:16][CH:15]=[C:14]([CH3:18])[C:13]=1[CH3:19])([O-:11])=[O:10].[N:20](OCCCC)=[O:21]>C(O)(=O)C.O>[CH3:18][C:14]1[CH:15]=[CH:16][CH:17]=[C:12]([N+:9]([O-:11])=[O:10])[C:13]=1[CH:19]=[N:20][OH:21]
1200 ml of anhydrous DMF are initially charged in a 4 l reaction flask and cooled to −40° C. At this temperature, 336.5 g (4.56 mol) of potassium methoxide (95%) are added with stirring and suspended. A mixture of 300 g (1.92 mol) of 3-nitro-o-xylene (97%) and 274 g (2.52 mol) of n-butyl nitrite (95%) is subsequently added dropwise at −40° C. over a period of 7 hours (if the mixture is cooled appropriately, the duration of this addition can be reduced at will). By HPLC, it is checked that the starting material has been converted completely. The reaction discharge is subsequently added with stirring to a mixture of 300 ml of water and 300 ml of glacial acetic acid, at from −5 to 0° C. The reaction mixture is then poured into 6 kg of ice-water and the solid is separated off by filtration and washed twice with 500 ml of water each time.
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