P-Nitrobenzenesulfonate

Asymmetric introduction of azide to the a-position of a carbonyl has been achieved by several methods. These include amine to azide conversion by diazo transfer,2 chiral enolate azidation,3 and displacement of optically active trifluoromethanesulfonates,4 p-nitrobenzenesulfonates,5 or halides.6 Alkyl 2-azidopropionates have been prepared in optically active form by diazo transfer,2 p-nitrobenzenesulfonate displacement,5 and the Mitsunobu displacement using zinc azide.7 The method presented here is the simplest of the displacement methods since alcohol activation and displacement steps occur in the same operation. In cases where the a-hydroxy esters are available, this would be the simplest method to introduce azide. 

After protection, the a-hydroxy esters can be reduced by DIBAL-H into O-protected a-hydroxyaldehydes that are very useful synthetic intermediates (e.g., leukotrienes,7-9 ionophore antibiotics,10 insect pheremones,11 etc.). The secondary hydroxyl group of the a-hydroxy esters may also be substituted with inversion of configuration after activation as triflates of nosylates (p-nitrobenzenesulfonates) to give a-alkyl esters12 ora-amino esters.13... 

The formation of ethoxycarbonylnitrene from the anion of iV-(ethoxycarbonyl) 0-(p-nitrobenzenesulfonyl)hydroxylamine 3n by elimination of p-nitrobenzenesulfonate was already reported (equation... 

Problem 11.62 Explain these observations (a) p-Nitrobenzenesulfonic acid is formed from the reaction of p-nitrochlorobenzene with NaHSO, but benzenesulfonic acid cannot be formed from chlorobenzene by this reaction. (f>) 2,4,6-Trinitroanisole with NaOC H, gives the same product as 2,4,6-trinitrophenetole with NaOCHj. <... 

Cationic movements are given as percentages of the anionic movement (about 10 cm) of p-nitrobenzenesulfonic acid on the same strip with 2,3,6-tri-O-methyl-D-glucose as non-migrating marker. The electrolyte solution was a 0.1 M solution of the metal acetate in 0.2 M acetic acid. 

Alunni, S., Pero, A., Reichenbach, G., Reactivity of ions and ion pairs in the nucleophilic substitution reaction on methyl p-nitrobenzenesulfonate. J. Chem. Soc., Perkin Trans., 21998, 1747-1750. 

SN2 reactions between methyl p-nitrobenzenesulfonate and halide ions and amines in several different ionic liquids have been investigated.76 The rates of reaction can be understood using the Hughes-Ingold rules77 if one considers the ion-ion interactions and ion-dipole interactions that occur with the ionic liquid solvent. Changing the ionic liquid solvent can reverse the relative reactivity of Cl-, Br-, and I- nucleophiles. 

We could not make m-bromochlorobenzene in good yield this way because both Br and Cl are ortho,para-directing. Similarly, we could not prepare p-nitrobenzenesulfonic acid directly because both the nitro and sulfonic acid substituents are mefa-directing. 

Since iodide ion is a strong nucleophile, the action of iodides on cellulose tosylate, mesylate, and nitrate in ketones, and chlorodeoxycellulose in DMF or 2,5-hexanedione can generate iododeoxycellulose. In use of chlorodeoxycellulose, the chlorine substituents were almost completely replaced by iodide in 2,5-hexanedione. The iododeoxycellulose thus prepared was 6-dexoy-6-iodocellulose. lododeoxycelluloses having iodo substituents at C2 and C3 were also prepared by treating various sulfonates having a DS higher than 1.0 or 6-0-trityl-2(3)-p-nitrobenzenesulfonate of cellulose with sodium iodide in DMF. Ishii [134,135] succeeded in the almost quantitative preparation of 5,6-cellulosene acetate by the treatment of acetylated 6-deoxy-6-iodocellulose (DS 0.8) with 1,8-diazobicyclo [5,4,0]undec-7-ene in DMF. 

Nitrobenzene can be produced on a technical scale in yields up to 98 percent by nitration of benzene with mixed acid. The sulfuric acid serves as a solvent and generates the nitronium ion, which is the attacking electrophile [5]. Nitrobenzene itself may be further nitrated with a mixed acid giving m-dinitrobenzene. The o- and p-dini-trobenzenes are removed as water-soluble products by treating the nitration product with aqueous sodium sulfite, sodium 0- and p-nitrobenzenesulfonates being formed. The residual m-nitrobenzene is separated from the aqueous layer, washed with water and finally dried [11]. 

Very thorough studies have been carried out on the deamination of the epime-ric 4-t-butylcyclohexylamines (226)138 20S 208 the silver-assisted dehalodecarboxy-lation of the analogous chloroformates (22 7)201, and the solvolysis of the corresponding p-nitrobenzenesulfonates (22S)213. Although ion pairs play an important role in some of the deamination reactions (cf. Section 4.3.2), cis- and trans-(226) clearly... 

The second synthesis of cephalotaxine was reported by Semmelhack and co-workers (24), also in 1972. Their convergent strategy involved the alkylation of spirocycle 49, prepared in several steps from p)nTolidone 45, with p-nitrobenzenesulfonate ester 50, prepared from piperonal in 45-55% overall yield as shown in Scheme 2. The resulting key intermediate, 51a (X = Cl), was converted to ( )-cephalotaxinone (22), initially through an aryne intermediate. Route I, Scheme 3, in 15% yield. Cephalotaxinone was then converted to ( )-cephalotaxine (1) upon reduction with diisobutyl-aluminum hydride. The Semmelhack group expended considerable effort studying the conditions of the nucleophilic aromatic substitution (i.e., 51a-c... 

Table IV. Rate Constants and a-Deuterium KIEs in the Reaction of n-Octyl p-Nitrobenzenesulfonate with Quaternary Phosphonium Salts in Dry and Wet Chlorobenzene at 50 °C...

Methyl p-Nitrobenzenesulfonate, p-Nitrobenzene-sulfonic acid methyl ester. C,HTNO,S mol wt 217.20. C 38.71%, H 3.25%, N 6.45%, O 36.83%, S 14.76%. Reagent for selective methylation or cysteine residues in chemical modification of proteins Nakagawa, Bender, J. dm. Chem. Sac, 91, 1566(1969). Procedure Heinrikson. Biochem. Bio-phys. Res. Common. 41, 967 (1970). Prepd by the general method of reacting p-nitrobenzenesulfony] chloride with alcohols. See Morgan, Cretcher, J. Am. Chem Soc. 70, 375 (1948). 

The large variation in polymerization rates among the various 2-oxazoline monomers has been exploited for the preparation of quasi-diblock copolymers, namely, gradient copolymers with a narrow and steep monomer gradient, by statistical copolymerization of selected monomer combinations exhibiting large differences in reactivity. Such a one-pot quasi-diblock copolymer synthesis was first demonstrated for the statistical copolymerization of 2-phenyl-2-oxazoline and a much less reactive 2-perfluoroalkyl-2-oxazoline [174]. This living CROP (in nitromethane at 120 °C initiated by methyl p-nitrobenzenesulfonate) revealed complete consumption of the 2-phenyl-2-oxazoline after 2 min with only minor incorporation of the fluorinated monomer. Continuation of the polymerization for another 40 h led to full conversion of the fluorinated monomer. The... 

Nucleophilic substitution reactions in ionic liquids have recently been the subject of both synthetic [33] and kinetics and mechanistic studies [34]. Ionic liquids may be efficient promoting media for nucleophilic displacement reactions and important information about the ionic liquid properties has been obtained from the study of these reactions. The kinetic investigation of bimolecular substitution reactions of the halides on methyl p-nitrobenzenesulfonate, recently carried out by Wdton et al. [34] in several ionic media characterized by the same anion, [Tf2N] , and different cations ([BMIM]+, [BMMIMJ+ and [BMPY]+) or by the same cation, [BMIM] and different anions ([BF4] , [PFs] , [SbF ] and [Tf2N] ), has shovrathat the halides nucleophilicities depend on the ionic liquid structure (Scheme 5.1-7). 

Scheme 5.1-7 Bimolecular substitution reaction of methyl p-nitrobenzenesulfonate with halides.

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