[N+:1]([O-:4])(O)=[O:2].[C:5]([C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)(=[O:9])[CH2:6][CH2:7][CH3:8].[N+]([O-])(O)=O.S(=O)(=O)(O)O>S(=O)(=O)(O)O>[N+:1]([C:12]1[CH:11]=[C:10]([C:5](=[O:9])[CH2:6][CH2:7][CH3:8])[CH:15]=[CH:14][CH:13]=1)([O-:4])=[O:2]Concentrated nitric acid (40 ml) was added cautiously with cooling to concentrated sulphuric acid (100 ml) maintaining a temperature of −5° C. Another solution of butyrophenone (59.2 g, 0.47 mol) in concentrated sulphuric acid (140 ml) was made up with shaking, keeping the temperature at −5° C. (+/−5° C.). The former nitric acid/sulphuric acid solution was added portionwise over 45 min to the latter solution of ketone in sulphuric acid keeping the temperature at −10° C.(+/−5° C. during the addition and for a subsequent 30 min. The reaction mixture was poured onto crushed ice (1.5 l) and then extracted with diethyl ether (200 ml and then 3×100 ml). The combined organic extracts were washed with water and then aqueous saturated sodium hydrogen carbonate solution and dried (MgSO4) before concentrating in vacuo. The crude yellow oil crystallised after 16 h and was then purified by chromatography on silica gel (1 kg) eluting with hexane:diethyl ether (9:1) to give the title compound as a white solid (9.1 g, 10%).
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