P-nitrophenyl chloroformate

Alternatively, two phosgene equivalents were studied, methyl chloroformate and p-nitrophenyl chloroformate. When methyl chloroformate was used for the end game, N-carbamate 54 was obtained smoothly but subsequent cyclization to ben-zoxazinone 1 was sluggish. Furthermore, removal of the unreacted intermediate methyl carbamate 54 from Efavirenz was not trivial, thus we did not pursue this method. On the other hand, reaction of 53 and p-nitrophenyl chloroformate initially provided the corresponding p-nitrophenyl carbamate 55 under mild basic conditions (KHC03). Carbamate 55 was smoothly cyclized to 1 upon increasing... 

A recent study concerned the microwave-assisted parallel synthesis of di- and tri-substituted ureas utilizing dedicated 96-well plates in the CombiCHEM system [60], In a typical procedure, modification of the Marshall resin utilized was achieved by treatment with p-nitrophenyl chloroformate and N-methylmorpholine (NMM) in dichloromethane at low temperatures. The resulting resin was further modified by attaching various amines to obtain a set of polymer-bound carbamates (Scheme 7.48). 

On the other hand, polymeric carriers can also be modified to introduce reactive groups. Polysaccharides such as dextran and inulin may be activated [149] by periodate oxidation to create aldehyde groups, by succinic anhydride activation to create carboxylic groups, or by p-nitrophenyl chloroformate activation to create reactive ester groups. 

Recently, the Klok group also prepared side-chain PEG-coated surfaces for protein immobilization [201], They employed surface-initiated ATRP for the synthesis. Terminal hydroxyl groups of the PEGs were activated with p-nitrophenyl chloroformate, and subsequently 06-benzylguanine was bound. The 06-benzylguanine-functionalized PEG brushes were used to chemoselectively immobilize 06-alkylguanine-DNA-alkyltransferase fusion proteins with a defined orientation and surface density. 

In the first instance, p-nitrophenyl chloroformate was selected for the acylation of AIC (Step 1 in Scheme 20). Reaction of AIC hydrochloride (0.154 mole) in methylene chloride first with an excess of triethylamine (0.323 mole) and then with a solution of /I-nitrophcnyIchI<>roformate (0.169 mole) in methylene chloride at room temperature for 24 hr gave compound XXX (X = p-nitrophenoxy) in 93% yield. 

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

Pyridyl)ethyl-p-nitrophenyl carbonate, The reagent is prepared by reaction of (2-pyridyl)ethanol and p-nitrophenyl chloroformate. 

A typical preparation of the polycarbonates is shown for polymer III in Scheme I. 1,4-Benzenedimethanol is activated by reaction with two equivalents of p-nitrophenyl chloroformate in pyridine and the resulting symmetrical dicarbonate is then used in a polycondensation with an equimolar amount of 2-cyclohexen-l,4-diol in a solid-liquid phase-transfer catalyzed reaction with 18-crown-6 as catalyst and solid anhydrous potassium carbonate as base. Alternately, the same polymer can be prepared by condensation of bis(4-nitrophenyl)-2-cyclohexen-1,4-ylene dicarbonate [12] with 1,4-benzenedimethanol or through a variety of similar polycondensations using diol biscar bonylimidazolides [13,14]. 

An alternate procedure was used by Shafer et al. (1966) in their synthesis of p-nitrophenyl diazoacetate. The key to this synthesis was the use of a chloroformate intermediate. To a 16-fold excess of diazomethane in ether (10 ml) was added dropwise a solution of 48.4 mg of p-nitrophenyl chloroformate. After the solution stood overnight at 4°C, the excess diazomethane was removed under a stream of N2 and the ether evaporated under reduced pressure. The residual yellow oil was dissolved in 2 ml of benzene and chromatographed on an alumina column using benzene as the eluant. The first fraction contained 48 mg of product which could be recrystallized from chloroform-hexane (m.p. 92-94°C). These authors reported that several other diazoacetates can be prepared by this procedure. 

In another example, p-nitrophenyl chloroformate was required to introduce a sophisticated carbamate function in a multi-steps synthesis of retroviral protease inhibiting compounds (Ref. 26). The structure of the intermediate carbonate is given in scheme 30. 

A second route (Method B in Scheme 36) involves the reaction of triphosgene with the deprotected terminal amine, providing chloroformamides that lose HCl to give isocyanates. A urea derivative is formed by adding an anthranilate or an an-thranilic acid derivative. Alternatively, an activated carbamate can be produced from p-nitrophenyl chloroformate as the reactive intermediate (Method C in Scheme 36). 

Preparation. The reagent is prepared1 by reaction of 3,5-dimethoxybenzoic acid (Aldrich) with lithium aluminum hydride and acylation of the resulting 3,5-di-methoxybenzyl alcohol with p-nitrophenyl chloroformate. 

Blocking of OH-groups fi-Benzoylpropionic acid. p-Nitrophenyl chloroformate. 

Nitro-2-methyl-1,3-propanediol, 12 2-Nitro-2-methyl-l-propanol, 12 2-Nitronaphthalene, 329 Nitronium tetraiiuoroborate, 296-297 p-NitrophenoI, 29, 176, 297 p-Nitrophenyl acetate, 297 p-Nitrophenyl azide, 333 p-Nitrophenyl chloroformate, 142, 297-298 p-Nitrophenyl esters, 297 p-Nitrophenylindazole, 334 p-NitrophenyIthymidine-3 -carbonate, 297,... 

Hydroxyl group Adamantane-l-carboxylic acid chloride. 0-Benzoylpropionic acid. Ethyl vinyl ether. 4-Methoxy-5,6-dihydro-2H-pyrane. p-Nitrophenyl chloroformate. 

Liskamp and coworkers [64] also reported the use of p-nitrophenyl carbamate derivatives obtained by reaction of Boc-protected iV-substituted ethylenediamines with p-nitrophenyl chloroformate for the synthesis of ureapeptoids. 

The anfi-Markownikoff-hydration of carbon-carbon double bonds hydroboration-oxidation has been supplemented by a remarkably simple and likewise stereospecific Markownikoff-hydration achieved by a one-step oxymercuration-demercuration p-Nitrophenyl chloroformate has been recommended for the protection of hydroxyl groups in nucleosides... 

Sigma-Aldrich in Buchs, Switzerland, performed the condensation of 2-trimethylsi-lylethanol and p-nitrophenyl chloroformate to give 2-(trimethylsilyl)ethyl 4-nitrophe-nyl carbonate [4]. Reduction of residence time is the issue to high selectivity, as the product degrades and side products also form. In contrast to the conventional technology that needs 14h to accomplish the reaction, a microreactor that enhances selectivity accomplishes the same in about 18 min. The reason for the better microreactor performance is not detailed and if the process parameters (e.g. temperature) were changed. 

A group of activation reagents similar to GDI have been developed in Israel (11). They resemble phosgene and prodnce immobihzed enzymes with bonds identical to those produced by GDI. One of their advantages is that p-nitrophenyl chloroformate can be used to prepare an activated matrix that has the property of releasing the yellow p-nitrophenol anion as conphng occurs, thereby permitting one to easily monitor the reaction visnally ... 

The methyl hydrazide is prepared by allowing Ac-Ala-Ala-OBz (6.9 mmoles) to react (24 hr, room temperature) with methyl hydrazine (170 mmoles). When one equivalent of water is added and dioxane (85 ml) is used as the solvent, the hydrazide crystallizes from the reaction mixture. The desired product, Ac-Ala-Ala-NHNHCHs, is isolated from the isomeric hydrazide, Ac-Ala-Ala-NfCHsiNH, by recrystallization from ethanol. The coupling of the substituted hydrazide with p-nitrophenyl chloroformate to form Ac-Ala-AIa-Aala-ONp is carried out by the procedure described in Method I to give a 66% yield of product with m.p. 200°-202° (ethanol). 

Nitrophenylalanine peptides, 90 3-Nitro-5-phenylbenzofuroxan, 80 p-Nitrophenylcarbamyl groups, 627 p-Nitrophenyl chloroformate, 40,118,209, 210... 

Of poorer selectivity, but of some use, is p-nitrophenyl chloroformate. In the case of a cis-diol arrangement, chloroformates or diphenyl carbonate will react to form a cyclic carbonate ... 

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