P-nitrophenyl sulfate

Sulfate monoesters can react by dissociative paths, and this is the favored path. Whether such reactions are concerted or involve a very short-lived sulfur trioxide intermediate has been the subject of debate. ° Benkovic and Benkovic reported evidence suggesting that the nucleophile is present (though there is little bond formation) in the transition state for the reaction of amines with p-nitrophenyl sulfate. Alkyl esters of sulfuric or sulfonic acids normally react with C-0 cleavage only when this is disfavored, as in aryl esters, does one see S-0 cleavage. Sulfate diester... 

For species 11 we will use the intrinsic barrier for hydroxide addition to trimethyl phosphate, G = 19 (calculated using rate and equilibrium data from reference 100) and assume the same value for the attack of hydroxide at sulfur on dimethyl sulfate. This (nonobservable) rate will be estimated using a Brpnsted type plot from the rate constants for diaryl sulfates (diphenyl sulfate,and bis p-nitrophenyl sulfate), estimated from the rate for phenyl dinitrophenyl sulfate,assuming equal contributions for the two nitro groups. This gives ftg = 0.95, and thus for dimethyl sulfate log k = 11.3... 

Numbers used in this cycle AG° for dissociation of sulfuric acid to sulfur tri-oxide AG° for hydrolysis of bis-p-nitrophenyl sulfate, estimated as described above AG° for hydrolysis of mono-p-nitrophenyl sulfate AG° for esterification to give pNP0S02, estimated as described above AG° for ionization of protonated SO3, estimated as described above AG° for ionization of p-nitrophenol. )... 

Numbers used in the cycle AG° for addition of hydroxide to p-nitrophenyl sulfate, see above AG° for proton transfer from p-nitrophenyl sulfate to hydroxide, based on pA a values AG° for ionization of the monoanionic adduct of p-nitrophenyl sulfate, estimated by the method of Branch and Calvin, supplemented by the difference in pATa between sulfuric acid and p-nitrophenyl sulfate.)... 

It is clear that the water reaction of p-nitrophenyl sulfate monoanion should occur by a dissociative mechanism, because 17 is too high in energy. (This was... 

FIGURE 2. Br0nsted-type plot for reactions of methyl p-nitrophenyl sulfate with amines. The a-nucleophiles are shown as soUd circles. Data taken from Buncel, Chuaqui and Wilson, J. Org. Chem., 45, 3621 and reprinted with permission. Copyright (1980) American Chemical Society... 

The arylsulfatase substrate p-nitrophenyl sulfate is used together with lead nitrate in a manner analogous to the Gomori reaction (Example 1.5). 

Although metal-promoted hydrolysis of phosphate esters is a topic of very current interest (Section 61.4.4), little work has been published dealing with the effects of metal ions on the hydrolysis of sulfate esters. The acid-catalyzed hydrolysis of aryl sulfates has been shown to occur by an A-1 mechanism (Scheme 34)." Nucleophilic catalysis by amines has been observed in the hydrolysis of p-nitrophenyl sulfate and intramolecular carboxyl group catalysis occurs with salicyl sulfate as with salicyl phosphate. 

Peptide synthesis /-Amyl chloroformate. Bis-(2,4-dinitrophenyl)carbonate. Bis-o-phenylene pyrophosphite. i-Butyl chloroformate. sec-Butyl chloroformate. /-Butyl chloroformate. /-Butyl 2,4,5-trichlorophenyl carbonate. CopoIy(ethylene-N-hydroxymaleimide). N,N-Diethyl-I-propynylamine. Di-(p-nitrophenyl)sulfate. Ethoxyacetylene. N-Ethoxycarbonyl-2-ethoxy-l,2-dihydroquinoline. N-Ethylbenzisoxazolium fluoroborate. Ethyl chloroformate. N-Ethyl-5-phenylisoxazolium-3 -sulfonate. N-Hydroxysuccinimide trifluoroacetate. Methyl-morpholine. 4-Methylthiophenol. p-Nitrophenol. Oxalylchloride. Pentachlorophenol. Pentamethylbenzyl chloride. /-Pentyl chloroformate. Phenacyl bromide. Polyhexamethylene carbodiimide. Tetraethyl pyrophosphite. 1,2,4-Triazole. 

Sulfate ester hydrolysis (p-nitrophenyl sulfate, 1 x 10 ) Phosphomonoesters hydrolysis (p-nitrophenyl phosphate, 1.1)... 

Two-dimensional free energy surfaces for the hydrolysis of p-nitrophenyl phosphate and sulfate have been examined and, together with other calculations, the experimentally observed activation barriers have been reproduced with reasonable accuracy (i.e. within 3.5kcalmol ). Moreover, it was demonstrated that, counterintuitively, hydrolysis of p-nitrophenyl sulfate proceeded through a more expansive pathway than its phosphate analogue. ... 

Reactions at sp centers are associated with small (<10) alpha effects, as typified by those illustrated in Figure 3.3. On the other hand, the rather small value of the alpha effect for the reaction of methyl p-nitrophenyl sulfate is contrasted with the reaction of p-nitrophenyl acetate at an sp center, with butane-2,3-dionemonoximate (Ox )... 

FIGURE 3.3 Br0nsted-type plot of log versus p for the reaction of nucleophiles with methyl p-nitrophenyl sulfate. The a-nucleophiles are shown as solid circles. Source Buncel et al. (1980) by permission of the American Chemical Society. 

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