4-Nitrophenyl carbonates

Benzyl 4-nitrophenyl carbonate [13795-24-9] M 273.2, m 78-80 . Dissolve in Et20, wash with H2O (3x) and satd aq NaCl, dry (MgS04), evap in vac and recryst residue from a small vol of MeOH, m 78-79°. Alternatively dissolve in Et20, wash with N HCI (2x), 0.5N NaHC03 (4x) then H2O, dry (Na2S04), evap Et20 and recryst residue from CgHg-pet ether, m 79-80°. [Khosla et al. Indian J Chem 5 279 7967 Wolman et al. J Chem Soc (C) 596 1 976.]... 

Bis-(4-nitrophenyl) carbonate [5070-13-3] M 304.3, m 142-143 . Dissolve in CHCI3, wash with 2N NaOH (3 x) and once with cone HCl, dry (Na2S04), evaporate and crystallise from toluene (authors say 15 vols of benzene, prisms). [Helv Chim Acta 46 795 1963.]... 

The carbamate, prepared from the 4-nitrophenyl carbonate, is cleaved by reduction with dithiothreitol (DTT) and TEA to give the aniline, which triggers fragmentation, releasing the amine. ... 

Amino acids are protected as the 4-nitrophenyl carbonate (H2O, dioxane, 54-85% yield) and cleaved by reduction of the azide with SnCl2. The group is stable to the conditions normally used to cleave a BOC group, but it is not expected to be stable to a large number of strongly reducing conditions. ... 

The DMB carbamate can also be introduced through the 4-nitrophenyl carbonate. " It has been prepared from an isocyanate and 3, 5 -dimethoxybenzoin. The synthesis of a number of other substituted benzoins as possible protective groups has been described. ... 

The kinetics of the cyclization of 4-substituted benzamidoxime 4-nitrophenyl carbonates (34 X = H, Me, OMe, Cl, NO2) in the pH range 8-11 to yield the corresponding heterocycles (35) have been studied. At acidic pH, cyclization does not occur and the hydrolysis reaction predominates. 

Scheme 11 Formation of a Urethane Linkage in a Peptide by Coupling an N -Free Peptide with a 4-Nitrophenyl Carbonate I471...

Carbamate-bound guanidines have been prepared by the condensation of amines with thioureas linked to insoluble supports as carbamates [519]. The direct reaction of guanidines with resin-bound carbonates or other alkoxycarbonylating agents requires the use of chloroformates or other reactive carbonic acid derivatives [520,521], Carbamate-bound amidines (Entries 7 and 8, Table 3.28) have been prepared by the reaction of amidines with resin-bound 4-nitrophenyl carbonates (0.9 mol/L amidine in DMF/DIPEA, > 4 h [522-524]). 

Wang resin bound 4-nitrophenyl carbonate is a convenient intermediate for the attachment of amines to polystyrene as carbamates (see Experimental Procedure 14.2). Aliphatic amines [82-87], ammonia [88], and amino acids [89] react exothermically with this support, whereas anilines generally require catalysis and/or long reaction times (Entry 3, Table 14.7). For the immobilization of anilines as carbamates, Wang resin derived chloroformate [90-92] generally leads to better results than resin-bound 4-nitrophenyl carbonates. Amidines also react with polystyrene-bound 4-nitrophenyl carbonates to yield /V-alkoxycarbonyl amidines (Section 3.9 [93-95]). Support-bound alkoxycarbonyl hydrazines can be prepared by treating polystyrene-bound phenyl carbonates with hydrazine [96-98]. 

As alternatives to 4-nitrophenyl chloroformate, carbonyl diimidazole [100-102] or di-A-succinimidyl carbonate [103,104] can be used to convert polymeric alcohols into alkoxycarbonylating reagents suitable for the preparation of support-bound carbamates. Polystyrene-bound alkoxycarbonyl imidazole is less reactive than the corresponding 4-nitrophenyl carbonate, and sometimes requires heating to undergo reaction with amines. Additional activation of these imidazolides can be achieved by N-methylation (Entry 9, Table 14.7). 

Carbamates can also be prepared by treating support-bound amines with alkoxycarbonylating reagents such as chloroformates or aryl carbonates. Chloroformates or dicarbonates (e.g. Boc20) should not be used in large excess for the alkoxycarbonyla-tion of primary amines because double derivatization can occur [119]. Less reactive reagents include 4-nitrophenyl carbonates and A-succinimidyl carbonates (Entries 2 and 3, Table 14.8). 

Enantiomerically pure aminoalcohols, which are readily available by reduction of a-amino acids, can be converted into alkoxycarbonylating reagents suitable for the solid-phase synthesis of oligocarbamates (Figure 16.26). Particularly convenient alkoxycarbonylating reagents are 4-nitrophenyl carbonates, which can be prepared from alcohols and 4-nitrophenyl chloroformate, and which react smoothly with aliphatic primary or secondary amines to yield the corresponding carbamates. 

The first example that describes imprinted catalytic microgels was reported in 2004 by Resmini et al. [71], which described the synthesis of soluble acrylamide-based microgels with hydrolytic activity towards 4-acetamidophenyl 4-nitrophenyl carbonate (102). The imprinting strategy was based on the corresponding phosphate TSA (103). Literature data demonstrated that arginine (104) and tyrosine (105) are... 

A kinetic study of the aminolysis of / -cresyl / -nitrophenyl carbonate by B11NH2 in C6H6 at 27 °C in the presence of pyridine, Et3N, or imidazole has shown that each of the three bases are very effective catalysts.38 A concerted mechanism of aminolysis of di(4-nitrophenyl) carbonate (37 X = N02) by anilines at 25 °C in 44% EtOH-water was indicated by a linear Br0nsted-type plot showing ft = 0.65. However, the aminolysis of two related compounds, 4-methylphenyl (37 X = Me) and 4-chlorophenyl 4-nitrophenyl carbonate (37 X = Cl), with = 0.85 and 0.78, respectively, proceeded by a stepwise mechanism.39... 

More useful is the conversion of dextran with ethyl chloroformate or 4-nitrophenyl chloroformate carried out in DMF/IiCl to give the corresponding carbonates [356]. Analysis of the total carbonate content and the content of 4-nitrophenyl carbonate moieties during the course of the reac-... 

Fig. 52 Binding of phenylamine and tyramine to dextran via functionalisation with 4-nitrophenyl carbonate and subsequent formation of a carbamate...

A solution of 500 mg (1.76 mmol) of (2S,3S,5S)-2,5-diamino-l,6-diphenyl-3-hydroxyhexane and 480 mg (1.71 mmol) of ((5-thiazolyl)methyl)-(4-nitrophenyl)carbonate in 20 ml of THF was stirred at ambient temperature for 4 hours. After removal of the solvent in vacuo, the residue was purified by silica gel chromatography using first 2% then 5% methanol in chloroform to provide a mixture of the two desired compounds. Silica gel chromatography of... 

Recently we have reinvestigated (16) the activation of dextran with 4-nitrophenyl chloroformate (VII). The content of the 4-nitrophenyl carbonate groups in activated dextran can be easily determined... 

Sigma-Aldrich performed the condensation of 2-trimethylsilylethanol and p-nitrophenyl chloroformate to give 2-(trimethylsilyl)ethyl 4-nitrophenyl carbonate... 

Historically, the first practicable reagent for the synthesis of N -Boc amino acids, tert-butyl 4-nitrophenyl carbonate (52), was developed by Anderson and McGregorb (Scheme 25). Due to the low reactivity of this mixed carbonate, drastic reaction conditions are required and yields remain unsatisfactory because of the difficult and laborious separation of the byproduct 4-nitrophenol. Alternative mixed carbonates have been proposed such as tert-butyl 2,4,5-trichlorophenyl carbonate (53),b32] lert-butyl pentachlorophenyl carbonate (54),b33] tert-butyl 2-pyridyl carbonate (55)0-tert-hvXy 5-4,6-dimethylpyrimidin-2-yl thiocarbonate (56).b3 1 With the latter two reagents the byproducts, pyridin-2-ol and 4,6-dimethylpyrimidine-2-thiol, respectively, are acid soluble and, thus, readily removed. 

A mixture of H-Ala-OH (0.53 g, 6 mmol), 2-nitrobenzyl 4-nitrophenyl carbonate (2.3 g, 7.2 mmol), 2M NaOH soln (6.0 mL), and THF (20 mL) was stirred for 24 h at rt. On removal of the THF, sodium 4-nitrophenolate precipitated. This was filtered off and washed with NaHC03 soln. The filtrate was acidified with 2M HCl to pH 5-6, and the excess reagent and 4-nitrophenol were removed by extraction with Et20. The remaining aq phase was acidified to pH 1 and extracted thoroughly with Et20 or EtOAc. Removal of the solvent afforded Z(2-N02)-Ala-0H as light yellow crystals yield 1.2 g (75%) mp 131 °C. 

C-Terminal peptide carbamates are prepared by reaction of the mixed succinimidyl carbonate of the N -protected amino alcohol (e.g., Fmoc-Phe-o-CO-OSu) obtained from the N -protected amino alcohol with DSC in the presence of DMAP, without isolation, with an aminomethyl resin (e.g., H-PAL-Nle-PEG-PSty).f l Standard Fmoc/tBu assembly of the remaining sequence is subsequently performed. Cleavage of the resin with TFA/H2O (19 1) affords the peptide carbamates with good purity. Use of isolated and purified 4-nitrophenyl carbonate monomers has also been described for the same purpose.f l... 

By converting the [(Z)-4-hydroxybut-2-enyl]oxy)acetyl resin 9 into its 4-nitrophenyl carbonate derivative, an allyloxyacetyl resin 10 is obtained which has been used to prepare pseudoargiopinine III by SPPS (Scheme 5).b l... 

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