Nitroaryl halides

The reduction of o-nitrophenyl acetic acids or esters leads to cyclization to oxindoles. Several routes to o-nitrophenylacetic acid derivatives arc available, including nitroarylation of carbanions with o-nitroaryl halides[2l,22] or trif-late[23] and acylation of o-nitrotoluenes with diethyl oxalate followed by oxidation of the resulting 3-(u-nitrophenyl)pyruvate[24 26]. 

Another use for reagent is for reductive elimination of halogen from at least some nitroaryl halides, for example picryl iodide " ... 

Reduction versus Substitution in the Reaction of Nitroaryl Halides with Alkoxide Ions... 

Whereas in the reaction of TNB with phenoxide ion the adduct from C attack is obtained, picryl chloride and other nitroaryl halides react with phenoxide ion to give only 14, the product of O attack. This is in fact the normal route for the formation of picryl phenyl ethers, and no instance of a picryl halide... 

Sulfonic acids can also be obtained by the Strecker synthesis from sodium sulfite and aryl halides that contain reactive halogen. Thus o-formylbenzene-sulfonic acid is formed in very good yield when o-chlorobenzaldehyde is heated under pressure with sodium sulfite,354 2-formyl-4-nitrobenzenesulfonic acid is formed on merely boiling 2-chloro-5-nitrobenzaldehyde with alcoholic sodium sulfite solution.355 The nitro group of nitroaryl halides may also be reduced to an amino group (cf. page 626) using polyhalo compounds leads to poly sulfonic acids.356... 

Several versions of palladium-catalyzed coupling reactions have been used to convert o-nitroaryl halides to o-nitrophenylacetaldehydes or o-nitrobenzyl ketones. Coupling with trimethylsilylethyne gives aryl alkynes which can be converted to o-nitrophenylacetaldehyde enol ethers by sodium ethoxide (Scheme 21) <86CPB2362>. 

Particularly detailed mechanistic studies have been carried out on the reaction of amines with nitroaryl halides and nitroaryl ethers. Such reactions can be formulated in terms of the general addition-elimination mechanism. 

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