Aryl nitro compounds, sulfonation

Reaction of halo sulfonic acid esters with boranes 10-125 Alcoholysis of sulfonic acid derivatives 13-15 Vicarious substitution of aryl nitro compounds... 

In the aryl nitro compounds, the powerful electron-withdrawing (—1, -M) effect of the nitro group results in the sulfonation of nitrobenzene being more difficult than that of benzene. Early work claimed that heating nitrobenzene with excess chlorosulfonic acid (two equivalents) afforded m-nitrobenzenesulfonyl chloride, but under drastic conditions (150 °C, 20 hours) the only product was reported to be tetrachloro-/>-benzoquinone (chloranil). 

Alkyl halides are often used as substrates instead of alcohols. In such cases the salt of the inorganic acid is usually used and the mechanism is nucleophilic substitution at the carbon atom. An important example is the treatment of alkyl halides with silver nitrate to form alkyl nitrates. This is used as a test for alkyl halides. In some cases there is competition from the central atom. Thus nitrite ion is an ambident nucleophile that can give nitrites or nitro compounds (see 0-60).731 Dialkyl or aryl alkyl ethers can be cleaved with anhydrous sulfonic acids.732... 

While porphyrins are famed for their substitutional flexibility [39], available corroles were initially restricted to a few compounds with small alkyl substituents at the (3-pyrrole positions. However, the library of free-base corrole complexes has expanded greatly since the advent of new syntheses, [4CM-2] especially those which allowed for the synthesis of corroles with aryl or alkyl substituents at the meso positions [29, 43] with no (3-substituents. These can be derivatized by a variety of electrophilic substitution reactions [44-47] to place nitro, formyl, sulfonate, and halide groups on the ring. 

Simple alkencs that do undergo the Diels-Alder reaction include conjugated carbonyl compounds, nitro compounds, nitriles, sulfones, aryl alkenes, vinyl ethers and esters, haloalkenes, and dienes. In addition to those you have seen so far, a few examples are shown in the margin. In the last example it is the isolated double bond in the right-hand ring that accepts the diene. Conjugation with the left-hand ring activates this alkene. But what exactly do we mean by activate in this sense We shall return to that question in a minute. 

Simple alkenes that do undergo the Diels-Alder reaction include conjugated carbonyl compounds, nitro compounds, nitriles, sulfones, aryl alkenes, vinyl ethers and esters, haloaUc-... 

Various chlorodifluoromethyl p-substituted aryl ketones and sulfones have been evaluated for their potential as CF2 carbene sources for N- and 0-difluoromethylations of V-heterocyclic compounds and phenols.Electron-poor sulfones, especially p-chloro- and p-nitro-substituted sulfones, proved to be the most powerful O-difluoromethylating agents, the corresponding difluoromethylated phenols being obtained in good to excellent yields. 

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... 

Odier diemistries that have been employed as photoadd generators in chemically amplified resist compositions include imino sulfonates (22), 4-nitro-benzenesulfonic add derivatives (23), disulphone compounds 24), sulfonyl substituted diazomethanes (25), dibenzyl sulfones 26), and aryl-bu-trichloro-methyl-s-triazines (27). 

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