2.4.6- Trinitrochlorobenzene, reaction

It is of interest to note that 2,4,6-trinitrochlorobenzene reacts similarly with 49 to give the cation of 138 isolated as the perchlorate. In the reaction of the enamino ketone (50) with trichloroacetyl chloride (77) the chloro-... 

Similar reaction of dithiocarboxylic acids 75 with 2,4,6-trinitrochlorobenzene (76) in ethanol at 0°C yields thioesters 77, which are then cyclized at room temperature to the final product 78 (77JCS(P1)1273). 2-Oxo- and 2-iminocy-clopentane derivatives 79 provided compounds 80a and 80b, respectively (Scheme 13) (73JCS(P1)1009, 75JCS(P1)1277). 

Compound 432, which can be easily prepared from trinitrochlorobenzene (76), treated with triethylamine in dipolar aprotic solvents provided good yield of the denitrocyclization product 433 (80JCS(P1)2205). Reaction of 2,3,5,6-tetra-chloronitrobenzene (434) with various 1,2-diamines under high pressure provided mixtures of the corresponding open products of the nitro group displacement, e.g. 435, and cyclized products, e.g. 436 (Scheme 69). Compound 436 was formed by denitrocyclization reaction, since compound 435 did not cyclize under the used conditions (94BCJ196, 95BCJ3227). 

As we ve seen, aromatic substitution reactions usually occur by an electrophilic mechanism. Aryl halides that have electron-withdrawing substituents, however, can also undergo nucleophilic aromatic substitution. For example. 2,4,6-trinitrochlorobenzene reacts with aqueous NaOH at room temperature to give 2,4,6-trinitrophenol. The nucleophile OH- has substituted for Cl-. 

Trinitrochlorobenzene (picryl chloride) (87) can be prepared from the nitration of 2,4-dinitrochlorobenzene with nitronium tetrafluoroborate or mixed acid composed of fuming nitric acid and oleum. Picryl chloride is also synthesized from the reaction of phosphorous oxychloride with the pyridinium salt of picric acid. ... 

Trinitrobenzene is formed by of decarboxylation of trinitrobenzoic acid. It can also be prepared from trinitrochlorobenzene by reduction with copper in alcohol. Further nitration of dinitrobenzene also yields trinitrobenzene, but the reaction must be carried out under very severe conditions (high S03-concentration in the mixed acid, high nitration temperature), and the yields are low. 

Pendant chalcone groups on polymers behave similarly to pendant cinnamate groups. Thus, photocross-linkable polymer can be formed, for instance, from poly(vinyl alcohol) by a reaction with 4 -substituted-4-caboxychalcone in homogeneous dimethyl formamide solution, using 2,4,6-trinitrochlorobenzene as the condensing agent [155]. 

We also see in these examples that the temperature required to bring about the reaction is related to the number of ortho or para nitro groups. Of the three compounds, o-nitrochlorobenzene requires the highest temperature (/>-nitrochlorobenzene reacts at 130 °C as well) and 2,4,6-trinitrochlorobenzene requires the lowest temperature. 

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