Nitropyridines—continued 1-oxides

Dimethyl-4-nitropyridine-N-oxide-dimethyl sulfate adduct (220 g, 0.75 mole) was dissolved in methanol (1.0 Itr) and the solution heated to reflux. A solution of ammonium persulfate (140 gm) in water (200 ml) was added dropwise over 4 hours after which reflux was continued for 4 hours. Methanol was distilled off under reduced pressure and the residue was basified to pH 10 by addition of caustic lye (105 ml). The mixture was extracted with dichloromethane (2 times 400 ml). The dichloromethane layer was dried over sodium sulfate and filtered. The product was used as its solution in dichloromethane for the next reaction. 

Chloro-3-nitropyridine [5470-18-8] M 158.5, m 100-103°, 101-102°, 103-104° (sublimes), pK -2.6. Forms needles from H2O. Purified by continuous sublimation over a period of 2 weeks at 50-60°/0.1mm [Barlin J Chem Soc 2150 1964]. The N-oxide has m 99-100°(from CH2Cl2-Et20). [Taylor and Driscoll J Org Chem 25 1716 I960-, Ochiai and Kaneko Chem Pharm Bull Jpn 8 28 I960.]... 

The synthesis of fluoroalkyl-substituted heterocycles is a subject of continuous interest this challenging issue has been presented in details in reviews [107,108]. It has been shown that trifluoromethyl carbanion, generated from (trifluoromethyl) trimethylsilane (the Ruppert reagent), adds easily to 2-chloro-3-nitropyridine. The produced o adducts can be oxidized with dimethyldioxirane (DMD) to form two isomeric 2-chloro-4-(and 6-)trifluoromethyl-3-hydroxypyridines (Scheme 30) [109]. 

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