2,4-Dinitrofluorobenzene

Aryldiaziridines (125), difficult to obtain by standard diaziridine syntheses, were prepared by arylation with 2,4-dinitrofluorobenzene (72JOC2980). 

Dinitrofluorobenzene, DABCO, DMF, 85% yield. When this group was used to protect an anomeric center of a carbohydrate, only the /3-isomer was formed, but this could be equilibrated to the a-isomer in 90% yield with K2CO3 in DMF. 

The dinitrophenyl group has been used to protect the imidazole — NH group in histidines (45% yield)" by reaction with 2,4-dinitrofluorobenzene and potassium carbonate. Imidazole —NH groups, but not a-amino acid groups, are quantitatively regenerated by reaction with 2-mercaptoethanol (22°, pH 8, 1 h)." The 2,4-... 

Dinitrofluorobenzene (Sanger s reagent) [70-34-8] M 186.1, m 25-27 , b 133 /2mm, 140-141 /5mm, d 1.483. Crystd from ether or EtOH. Vacuum distd through a Todd Column (see p. 174). If it is to be purified by distn in vacuo, the distn unit must be allowed to cool before air is allowed into the apparatus otherwise the residue carbonises spontaneously and an EXPLOSION may occur. The material is a skin irritant and may cause serious dermatitis. 

One of the historically most significant examples of aromatie nueleophilie substitution is the reaetion of amines with 2,4-dinitrofluorobenzene. This reaetion was used by Sanger to develop a method for identifieation of the N-terminal amino acid in proteins and the proeess opened the way for struetural eharacterization of proteins and other biopolymers. 

Phenols Apply sample solution and spray with saturated sodium methylate solution and then treat with 4% 2,4-dinitrofluorobenzene in acetone and heat to 190°C for 40 min. Chromatograph the dinitro-phenyl ethers so produced. [79]... 

Acid fluondes such as oxalyl fluoride, tnchloroacetyl fluonde, propionyl fluonde, as well as Sanger s reagent, 2,4-dinitrofluorobenzene, easily cleave N,N-acetals (aminals) to give high yields of fluoromethyldialkylamines [82] (equation 20) (Table 5)... 

The weakly nucleophilic nng nitrogen of unsubstituted 2-aminothiazole replaces the fluorine atom of 2,4-dinitrofluorobenzene, whereas in 5-methyl 2 ami-nothiazole, the 2-ammo function acts as the nucleophile [62] (equation 31)... 

The arylation of morpholinocyclohexene with 2- or 4-chloroquinoline N-oxide or 4-chloropyridine N-oxide and benzoyl chloride led to cyclohexanone a-substituted with the respective chloroquinolines or 4-chloropyridine (691). 2,4-Dinitrofluorobenzene reacted with 2-benzylidene-3-methylbenzothiazoline to give the enamine arylation product (672). 

The DNP derivative, prepared from 2,4-dinitrofluorobenzene is released from the nitrogen with an anionic ion exchange resin." When used for histidine protection, the DNP group has been observed to migrate to nearby [ysine residues during Fmoc cleavage. ... 

Treatment of 228 with 2,4-dinitrofluorobenzene (227) provided 230. The assumed intermediate A -benzoyl-A -(2,4-dinitrophenyl)-A -phenylhydrazine (229) underwent the denitrocyclization reaction in its enol form (80JOC3677). Similar reaction is probably involved also in the thermal cyclization of antraquinone 231 leading to 232 (Scheme 35), which took place even during attempts to crystallize the compound (60T107). 

Nucleophilic aromatic substitution is much less common than electrophilic substitution but nevertheless does have certain uses. One such use is the reaction of proteins with 2,4-dinitrofluorobenzene, known as Sanger s reagent, to attach a "label" to the terminal NH2 group of the amino acid at one end of the protein chain. 

This characteristic dependence of rate on catalyst concentration was first observed by Bunnett and Randall28 for the reaction of 2,4-dinitrofluorobenzene... 

Bifunctional catalysis has also been observed by Pietra and Vitali35 for a more typical nucleophilic aromatic substitution reaction, that of 2,4-dinitrofluorobenzene and piperidine in benzene. For this reaction triethylamine does not have an... 

It has also been argued10,40 that the second mechanism (rapid, reversible interconversion of II and IV) cannot be general. The basis for this contention is the fact that electrophilic catalysis is rare in nucleophilic aromatic substitution of non-heterocyclic substrates, an exception being the 2000-fold acceleration by thorium ion of the rate of reaction of 2,4-dinitrofluorobenzene with thiocyanate... 

Another reagent, 2,4-dinitrofluorobenzene, also known as Sanders Reagent, has been used in a similar manner in the analysis of amino acids and amines (41). 

Dinitrofluorobenzene (86, X = F) is, because of its reactivity, much used for tagging the NH2 group of terminal amino-acids in protein end group analysis. Once it has reacted with the NH2 it is very difficult to remove again and will thus withstand the subsequent hydrolysis of the protein to its constituent amino-acids. 

Harada et al. started from preparing inclusion complexes by adding an aqueous solution of PEG bisamine (PEG-BA) to a saturated aqueous solution of a-CD at room temperature and then allowing the complexes formed to react with an excess of 2,4-dinitrofluorobenzene. They examined the product by column chromatography on Sephadex G-50, with DMSO as the solvent, and obtained the elution diagram shown in Fig. 46. They identified the first, second, and third fraction, respectively, as the desired product, i.e., a polyrotaxane, dinitrophenyl derivatives of PEG, and uncomplexed a-CD, by measurement of both optical rotation and UV absorbance at 360 nm for the first, UV absorbance at 360 nm for the second, and optical rotation for the third. 

Fluorobenzene-type compounds have been used as functional groups in homobifunctional crosslinking agents (Chapter 4, Section 4). Their reaction with amines involves nucleophilic displacement of the fluorine atom with the amine derivative, creating a substituted aryl amine bond (Reaction 9). Detection reagents incorporating reactive aryl chemistry include 2,4-dinitrofluorobenzene and trinitrobenzenesulfonate (Eisen et al., 1953). These compounds form... 

The use of periodate coupling chemistry for HRP first was introduced by Nakane and Kawaoi (1974 see also Nakane, 1975). In the first step of their protocol, the few amine groups on HRP were initially blocked with 2,4-dinitrofluorobenzene (DNFB) before periodate oxidation. 

Amines + 2,4-dinitrofluorobenzene Analytical method is improved by use of CTABr Wong and Connors, 1982... 

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