[N+:1]([O-:4])(O)=[O:2].[CH3:5][CH:6]([CH3:15])[C:7]([C:9]1[CH:14]=[CH:13][CH:12]=[CH:11][CH:10]=1)=[O:8].[N+]([O-])(O)=O.S(=O)(=O)(O)O>S(=O)(=O)(O)O>[CH3:5][CH:6]([CH3:15])[C:7]([C:9]1[CH:14]=[CH:13][CH:12]=[C:11]([N+:1]([O-:4])=[O:2])[CH:10]=1)=[O:8]Concentrated nitric acid (20 ml) was added cautiously with cooling to concentrated sulphuric acid (50 ml) maintaining a temperature of −5° C. Another solution of 2-methyl-1-phenyl-1-propanone (29.6 g, 0.2 mol) in concentrated sulphuric acid (70 ml) was made up with shaking, keeping the temperature at −5° C. The former nitric acid/sulphuric acid solution was added portionwise over 30 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 l) and then extracted with diethyl ether (3×100 ml). The organic extracts were washed with water (300 ml) and then brine (300 ml), dried (Na2SO4) and then concentrated in vacuo. The crude product was obtained as an orange oil (40 g) which was purified by chromatography on silica gel (450 g) eluting with hexane :diethyl ether (9:1) to give the title compound as a pale yellow solid (16.3 g, 42%), m.p.33-35° C.
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