4-Chloro-2-nitrophenyl phosphates

As is apparent from Fig. 1, the dianions of monoalkyl phosphates normally resist hydrolysis. However, for leaving groups whose conjugate acids exhibit a pKa < 5 in water, hydrolysis of the dianion becomes faster than that of the monoanion. Fig. 2 shows a pH profile characteristic of this situation. Whereas the hydrolysis rate of 2,4,6-trichlorophenyl phosphate (pKa of the phenol 6.1) still shows the typical monoanion preference as seen for methyl phosphates (Fig. 1), the dianion of 2,4-dinitrophenyl phosphate (pKa of the phenol 4.09) is hydrolyzed far faster than the monoanion 2-chloro-4-nitrophenyl phosphate represents an intermediate case (pKa of the phenol 5.45)6S). 

Substrate products can be classified as either soluble or precipitating. Soluble peroxidase substrates include o-phenylenediamine, which is converted into a yellow product 2,2 -azino-(3-ethyl)-benzothiazoline-sulfonic acid, which is converted into a green product and tetramethylbenzidine, which is converted into a blue product. Precipitating substrates for peroxidase include 4-chloronaphthol, which yields a blue precipitate and aminoethylcarbizole, which forms a red precipitate. Alkaline phosphatase is most frequently used with p-nitrophenyl phosphate to give a yellow-orange soluble product, or with 5-bromo-4-chloro-3-indo-lyl-phosphate p-toluidine salt to yield an insoluble blue product. 

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. 

Horse serum 7.5, 9.5 Diethyl 4-nitrophenyl phosphate (Paraoxon) and l-chloro-l-ethylcarbamoyl-l-propen-2-yl-dimethyl phosphate (Phosphamidon) W4... 

S 4-nitrophenyl phosphate -i- 6-chloro-9-( -D-ribofuranosyl)purine (Reversibility <3> [6]) [6]... 

There has been a useful review of phase-transfer catalysis in nucleophilic aromatic substimtion. A comparison has been reported of the reactions with nucleophiles of l-chloro-2,4-dinitrobenzene (substimtion) and 4-nitrophenyl diphenyl phosphate (dephosphorylation) in neutral micelles of dodecyl (10) and (23) polyoxyethylene glycol. In the substimtion reaction considerable amounts of ether may be formed by reaction with alkoxide ions at the micellar surface. Differences in reactivity of the two substrates are probably due to differences in their location in the micellar structures. ... 

CgHsClNOsPS 0,0-Dimethyl-0-(3-chloro-4-nitrophenyl)thio-phosphate, chlorthion 500-28-7... 

Nebularine has long been known as a metabolite of Clitocybe nebularis (383), revealing tuberculostatic and antimitotic activity (383-385). Few syntheses of this compound having a 9-(D-ribosyl)purine structure have been reported, namely, the Brown (386) approach, starting from a chloro-mercuri-6-purine and 2,3,5-tri-O-acetyl-D-ribofuranosyl chloride, the Fox (387) procedure, based on the transformation of inosine to nebularine via a desulfurization by Raney nickel of the thioinosine intermediate, and the Iwamura-Hashizume (384,388) method, in which nebularine and its N-7 isomer were synthesized simultaneously by the fusion of purine and tetra-O-acetyl-D-ribofuranose using bis(p-nitrophenyl)hydrogen phosphate as the catalyst. 

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