Halo nitro compounds

Indirect conversion of oximes to nitro compounds viact-halo nitro compounds has provided a useful method for synthesis of nitro compounds, as shown m Scheme 2 1... 

However, heterocycles containing thiophenols have not been reported. It has been observed that the thiophe-nolate ion undergoes nucleophilic attack by the halo/ nitro compounds more easily than the phenolate ion in displacement reactions [37-39]. The experimental result shows that the reactivity of 3-nitro-N-phenyl-phthali-mide with 4-methyl-thiophenolate (reaction 1) is 100 times faster than that of 4-methyl phenolate [40] (reaction 2) ... 

With some alkenes, the initial p-halo nitroso compound is oxidized by the NOCl to a P-halo nitro compound. Many functional groups can be present without interference (e.g., COOH, COOR, CN, OR). The mechanism in most cases is probably simple electrophilic addition, and the addition is usually anti, though syn addition has been reported in some cases. Markovnikov s rule is followed, the positive NO going to the carbon that has more hydrogens. 

Nitryl chloride (NO2CI) also adds to alkenes, to give p-halo nitro compounds, but this is a free-radical process. The NO2 goes to the less-substituted carbon. Nitryl chloride also adds to triple bonds to give the expected l-nitro-2-chloro alkenes. The compound FNO2 can be added to alkenes by treatment with HF in HNOa or by addition of the alkene to a solution of nitronium tetrafluoroborate (NOJBF4, see 11-2) in 70% polyhydrogen fluoride-pyridine solution (see also 15-37). 

It had been established several decades ago that the reaction of 1-chloro-l-ni-troethane with sodium nitrite in aqueous-alcohol medium is second order overall and first order in each reactant (Hawthorne 1956). 1-Deutero-l-chloro-l-nitroethane reacts more slowly than its lighter isotopomer. This means that the kinetic isotopic effect is observed. The reaction proceeds only in moderately alkaline media in strongly alkaline media it does not take place. Only those geminal halo nitro compounds, which carry hydrogen in the geminal position, can undergo the conversion. Based on these facts, Hawthorne (1956) suggested the Sn2 substitution preceded by the isomerization of the initial substrate into the aci-nitro form ... 

Halo Nitro Compounds Reaction of Steroid-5-enes with Nitrosyl Chloride... 

HALO-NITRO COMPOUNDS oxetanes-alkenes + ketones 15-63... 

It should, however, be noted that aromatic amino-nitro compounds are often more conveniently prepared by heating a halo-nitro compound with ammonia or an amine (e.g., N,N-dimethy -o- and -p-nitroaniline194) or by partial reduction of a polynitro compound (cf. pp. 463 et seq. and 575). 

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