2.4- Dinitrophenyl esters

Alternatively, weak acids and certain salts have been found to extend the lifetimes of inherently rapid reactions which occur with highly reactive esters, such as bis(2,4-dinitrophenyl) oxalate (95). A chemiluminescent demonstration based on the oxaUc ester reaction has been described (96) and the reaction has been developed iato a practical lighting system. 

Another significant use of 3-methylphenol is in the production of herbicides and insecticides. 2-/ f2 -Butyl-5-methylphenol is converted to the dinitro acetate derivative, 2-/ f2 -butyl-5-methyl-4,6-dinitrophenyl acetate [2487-01 -6] which is used as both a pre- and postemergent herbicide to control broad leaf weeds (42). Carbamate derivatives of 3-methylphenol based compounds are used as insecticides. The condensation of 3-methylphenol with formaldehyde yields a curable phenoHc resin. Since 3-methylphenol is trifunctional with respect to its reaction with formaldehyde, it is possible to form a thermosetting resin by the reaction of a prepolymer with paraformaldehyde or other suitable formaldehyde sources. 3-Methylphenol is also used in the production of fragrances and flavors. It is reduced with hydrogen under nickel catalysis and the corresponding esters are used as synthetic musk (see Table 3). 

We recently synthesized cationic polymers containing imidazole (e g. 68 (SZ811) and 69 (SZ11—3—3)] by reacting poly [N-(2,4-dinitrophenyl)-4-vinyl-pyridinium chloride] with histamine or histamine mixed with other amino derivatives ll8 The hydrolyses of neutral and anionic esters with the models followed saturation kinetics in alkaline media. 

S.P. solid-phase technique L.P. liquid-phase technique OPTcp pentachlorophenyl ester TEEP tetraethyl pyrophosphit OTCp trichlorophenyl ester ONp p-nitrophenyl ester ONSu N-hydroxysuccinimido ester OPFp pentafluorophenyl ester OQu 8-hydroxyquinyl ester OPy 3-hydroxy-pyridyl ester ODnp 2,4-dinitrophenyl ester DCC dicyclohexylcarbodiimide HOBn 3-hydroxy-4-oxo-3,4-dihydro-l,2,3-benzotriazin Opi JV-hy-droxypiperidine EEDQ 2-ethoxy-l-ethoxycarbonyl-l,2-dihydroquinoline Tos p-toluenesulfonyl PTC propanetricarboxylic acid OBu tm-butyl ester Nva norvaline Aha aminohexanoic acid Om ornithine... 

We have also investigated other oxalate esters as a potential means to improve the efficiency. The most commonly used oxalates are the 2,4,6-trichlorophenyl (TCPO) and 2,4-dinitrophenyl (DNPO) oxalates. Both have severe drawbacks namely, their low solubility in aqueous and mixed aqueous solvents and quenching of the acceptor fluorescence. To achieve better solubility and avoid the quenching features of the esters and their phenolic products, we turned to difluorophenyl oxalate (DFPO) derivatives 5 and 6 (Figure 14). Both the 2,4- and the 2,6-difluoro esters were readily synthesized and were shown to be active precursors to DPA chemiluminescence. In fact, the overall efficiency of the 2,6-difluorophenyl oxalate 5 is higher than for TCPO in the chemical excitation of DPA under the conditions outlined earlier. Several other symmetrical and unsymmet-rical esters were also synthesized, but all were less efficient than either TCPO or 2,6-DFPO (Figure 14). 

Efremov and coworkers observed that electron-donating groups promote the sulfoxide-sulfonate ester rearrangement in the molecular ions of 2,4-dinitrophenyl... 

The synthesis93 of N-(2,4-dinitrophenyl)-3-0-(tetra-0-acetyl-/ -D-glu-copyranosyl)-L-threonine methyl ester (131) involved a two-step procedure. First, formation of the intermediate, L-threonine orthoester 130 was achieved by treatment of tetra-O-acetyl-a-D-glucopyranosyl bromide (128) with the methyl ester of N-(2,4-dinitrophenyl)-L-threonine94 (129) under the conditions of the Koenigs-Knorr reaction (see next paragraph), and this was then converted into the L-threonine glycoside 131. 

A kinetic isotope effect 160/180 of 2% in the spontaneous hydrolysis of the 2,4-dinitrophenyl phosphate dianion, whose ester oxygen is labeled, suggests a P/O bond cleavage in the transition state of the reaction, and thus also constitutes compelling evidence for formation of the metaphosphate 66,67). The hydrolysis behavior of some phosphoro-thioates (110) is entirely analogous 68). 

As mentioned in Section II. C., the concerted bond cleavage of 1.2-dioxetane derivatives has been proposed to be of general importance in respect of the excitation step of a large number of chemiluminescence reactions. The first experimental results concerning simple dioxetanes were obtained by M. M. Rauhut and coworkers in their work on activated oxalic ester chemiluminescence 24>. From experimental data on the reaction of e.g. bis (2.4-dinitrophenyl)oxalate with hydrogen peroxide in the presence of rubrene, they concluded that 1.2-dioxetanedione... 

The initial study of the La3 +-catalyzed methanolysis of carboxylate esters163 reported the apparent second-order rate constant for La2 + ( OCH3)2-catalyzed methanolysis of some representative examples of aryl esters (2, 5 and 2,4-dinitrophenyl acetate (14)), phenyl benzoate (15) and three aliphatic esters, ethyl acetate, isopropyl acetate (16) and tert-butyl acetate (17). Given in Table 6 are the rate constants for the La3+ and methoxide-catalyzed methanolysis of these esters along with... 

The hydrolysis of sulfate monoesters has been studied increasingly in relation to sulfate group transfer in vivo. In general, the rate-enhancing effect on the sulfate cleavage is small even with hydroxamate- or imidazole-functionalized cationic micelles which are extremely effective for the hydrolysis of phenyl esters. Recently, Kunitake and Sakamoto (1979a) found that zwitterionic hydroxamate [47] cleaved 2,4-dinitrophenyl sulfate effectively in cationic and... 

The photosolvolysis of 3-nitrophenyl esters is the first example of the use of a light-sensitive protecting-group that has appeared in the literature. 3-Nitrophenyl and the more-sensitive 3,5-dinitrophenyl phosphoric esters undergo photohydrolysis (mercury lamp) to a phosphoric derivative and the corresponding nitrophenol an example of a synthetic application is presented in Scheme 30. 

Hubbard and Kirsch (1972) have recently proposed that histidine may act as a nucleophile in a-chymotrypsin acylation reactions of esters having a good leaving group (jO-nitrophenol). This suggestion was based on a similarity in p-value for acylation by p-substituted nitrophenyl and dinitrophenyl benzoates and nucleophilic attack on these compounds by imidazole, in contrast with less positive p-values for hydroxide ion catalysis. Hammett p-values for hydrolysis of substituted phenyl esters are given in Table 6 and show little apparent trend. The values for hydroxide ion and alcoholate ions are... 

From Table 8 it is obvious that the resolution always increases with an increase of the number of benzene rings and that riboflavine is a more powerful selector than the nucleotides, but not as good as TAPA. An interesting experiment shows that it is not always necessary to have the selector coated or bound to the solid phase but that it can sometimes be used as well, dissolved in the mobile phase. The n-dodecyl ester of N-(2,4-dinitrophenyl)-L-alanine is able to discriminate between the enantiomers of l-aza-[6]-helicene, when used as a chiral dopant in the mobile phase in HPLC on a reversed phase column 93) (see Table 9). The usefulness of this dopant must be due to the known ability of a dinitrophenyl moiety to form CT-complexes with polycyclic aromatic hydrocarbons the presence of a chiral site near this group causes resolution of helicenes, because the steric interactions in diastereomeric complexes will be quite different. 

Table 9. Resolution of l-Aza-6-Helicene by the n-Dodecyl Ester of N-(2,4-Dinitrophenyl)-L-Alanine as a Chiral Dopant in the Mobile Phase3 931...

Some exploratory experiments have also been carried out with some phosphate esters. Rate constants for one of these, dinitrophenyl-phosphate, are listed in Table VII. With this substrate, surprisingly, the intrinsic primary amines of the polymer seem to be acting in a turnover pathway, that is, are phosphorylated and then dephosphorylated, but this mechanism needs to be better substantiated. In any event it, it is clear that the rates in the presence of polymer are accelerated more than 103-fold with dinitrophenylphosphate. Even larger accelerations have been observed with other phosphate esters. 

Buckingham, D. A., and C. R. Clark, Metal-hydroxyde-promoted hydrolysis of activated esters. Hydrolysis of 2,4-dinitrophenyl acetate and 4-nitrophenyl acetate , Aust. J. Chem., 35,431-436 (1982). 

Fig. 2. pH-rate profiles for three representative esters at 39°C, ionic strength 1.0, on adjusted scales. A, x I07 min for 2,4,6-trichlorophenyl phosphate , Ahyd x 10 min-1 for 2-chloro-4-nitrophenyl phosphate O, byd x I04 min- for 2,4-dinitrophenyl phosphate. 

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