1,3,5-Trinitrobenzene, reactions with anilines

Conditions were found under which 2,4,6-trinitrostyrene adds nucleophiles (thio-phenol, aniline, and aliphatic amines) at the vinyl moiety to form the corresponding / -X-ethyl-2,4,6-trinitrobenzenes (X = PhS, PhNH, or R2N). In the reactions with primary aromatic amines, the initially formed adducts undergo an intramolecular replacement of the nitro group followed by aromatization of the indolines, giving rise to the corresponding A-substi Luted 4,6-dinitroindoles.219... 

In the presence of a strong base, such as Dabco or quinuclidine, the reaction of 1,3,5-trinitrobenzene with anilines in DMSO yields anionic adducts (9) as shown in Scheme 1. Kinetic studies show that due to the instability of the zwitterionic intermediates, (8), values of k i are high, leading to the condition k kB[B], so that the proton transfer step, kB, is rate limiting in the overall reaction. In the corresponding reactions of 4-nitrobenzofuroxan, which form the adducts (10), the slower interconversion of parent molecules and zwitterions, due to a higher intrinsic barrier, leads to the condition k x kB[B], so that proton transfer is only partially rate limiting 49... 

Synthesis.—Af-Phenylamides can be prepared from carboxylic acids by first esteri-fying the acid with 2-fluoro-1,3,5-trinitrobenzene followed by displacement of the ester group with aniline.This mild method is successful for a good range of acids, giving consistently high yields of the amide. A direct, high-yield conversion of esters into AW-disubstituted amides is by reaction with dimethylaluminium amides, which similarly convert lactones into hydroxyamides. ... 

It is quite common for the Sn reactions that at the addition step several nucleophiles are involved concurrently in addition and dissociation reactions. For instance, the reaction of trinitrobenzene with aniline in methanol yields first the methoxy O-adduct which is transformed slowly into the corresponding anilide N-adduct (Scheme 64) [6, 11, 200]. 

As a starting material for the preparation of sym-trinitrotriazidobenzene, 1,3,5-trichlorobenzene is used. It is obtained by the chlorination of aniline and the removal of the amino group. Nitration to the trinitro derivative is described in Vol. I. The final reaction is simple powdered 1,3,5,-trichloro-2,4,6-trinitrobenzene is added to an aqueous alcohol solution of sodium azide. The precipitated product is washed with alcohol and water and dried at a moderate temperature. The product so obtained may be purified by crystallization from chloroform. 

Evidence for the formation of Meisenheimer, or a a-complex, involving aniline as a nucleophile has been presented with 1,3,5-trinitrobenzene (TNB) by Buncel and coworkers107. Reactions of the TNB-methoxide ion adduct with a series of substituted anilines in DMSO solution yield new TNB-aromatic amine o-complexes (Scheme 12). 

This study reports on the reactions of ambident nucleophiles with electron-deficient nitroaromatic and heteroaromatic substrates anionic complex formation or nucleophilic substitution result. Ambident behavior is observed in the case of phenoxide ion (O versus C attack) and aniline (N versus C attack). O or N attack is generally kinetically preferred, but C attack gives rise to stable thermodynamic control. Normal electrophiles such as 1,3,5-trinitrobenzene or picryl chloride are contrasted with superelectrophiles such as 4,6-dinitrobenzofuroxan or 4,6-dinitro-2-(2,4,6-trinitrophenyl)benzotriazole 1-oxide (PiDNBT), which give rise to exceptionally stable a complexes. Further interesting information was derived from the presence in PiDNBT of two electrophilic centers (C-7 and C-l ) susceptible to attack by the ambident nucleophilic reagent. The superelectrophiles are found to exhibit lesser selectivity toward different nucleophilic centers of ambident nucleophiles compared with normal electrophiles. 

The exclusive formation of the C-1 adduct between 2,4,6-trinitroanisole and n-butylamine has actually been detected, as a transient intermediate en route to AT-(n-butyl)picramide, by a low-temperature flow n.m.r. experiment. Further kinetic data for the reversible reaction between the 1,3,5-tri-nitrobenzene-methoxide cr-complex and aniline in DMSO-MeOH solutions, yielding the 1,3,5-trinitrobenzene-anilide dissociative mechanism involving rate-determining interconversion of free TNB and the protonated anilide complex. The failure of aromatic primary amines by themselves to form stable (7-complexes with TNB is due to an unfavourable overall equilibrium represented by equation (3), while the additional presence of the strong base... 

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