Sulfonates displacement

Nucleophilic Displacement. Sulfones can be displaced by a variety of nucleophiles, the most common of which are the amines. Using this cleavage technique, a range of libraries, including pyrimidines, pyrimido[4,5-iflpyrimidines, purines, and triazines, each possessing a diverse variety of amine functionalities, have been prepared. 

Nucleophilic Displacement. - Sulfonate ester displacement reactions continue to be widely applied in amino-sugar syntheses. The 3-amino-S-thioglucofuranose derivative 20 was obtained from the corresponding allofuranose 3-mesylate by displacement with azide ion and reducdon (liAlHJ (see also section 2.6)." The 2,3-epimino-a-D-lyxopyranoside 21 was prepared in 11 steps from diacetoneglucose via 3-azido-3-deoxy-1.2-O-isoprc ylidene-a-D-glucofriranose. Key steps were... 

The reaction of alcohols with acyl chlorides is analogous to their reaction with p toluenesulfonyl chloride described earlier (Section 8 14 and Table 15 2) In those reactions a p toluene sulfonate ester was formed by displacement of chloride from the sulfonyl group by the oxygen of the alcohol Carboxylic esters arise by displacement of chlonde from a carbonyl group by the alcohol oxygen... 

As a variation on the base-catalyzed nucleopbilic displacement chemistry described, polysulfones and other polyarylethers have been prepared by cuprous chloride-catalyzed polycondensation of aromatic dihydroxy compounds with aromatic dibromo compounds. The advantage of this route is that it does not require that the aromatic dibromo compound be activated by an electron-withdrawing group such as the sulfone group. Details of this polymerization method, known as the Ullmaim synthesis, have been described (8). 

Delignification Chemistty. The chemical mechanism of sulfite delignification is not fully understood. However, the chemistry of model compounds has been studied extensively, and attempts have been made to correlate the results with observations on the rates and conditions of delignification (61). The initial reaction is sulfonation of the aUphatic side chain, which occurs almost exclusively at the a-carbon by a nucleophilic substitution. The substitution displaces either a hydroxy or alkoxy group ... 

The apphcation of bimolecular, nucleophilic substitution (S ) reactions to sucrose sulfonates has led to a number of deoxhalogeno derivatives. Selective displacement reactions of tosyl (79,85), mesyl (86), and tripsyl (84,87) derivatives of sucrose with different nucleophiles have been reported. The order of reactivity of the sulfonate groups in sucrose toward reaction has been found to be 6 > 6 > 4 > 1. ... 

Solvent for Displacement Reactions. As the most polar of the common aprotic solvents, DMSO is a favored solvent for displacement reactions because of its high dielectric constant and because anions are less solvated in it (87). Rates for these reactions are sometimes a thousand times faster in DMSO than in alcohols. Suitable nucleophiles include acetyUde ion, alkoxide ion, hydroxide ion, azide ion, carbanions, carboxylate ions, cyanide ion, hahde ions, mercaptide ions, phenoxide ions, nitrite ions, and thiocyanate ions (31). Rates of displacement by amides or amines are also greater in DMSO than in alcohol or aqueous solutions. Dimethyl sulfoxide is used as the reaction solvent in the manufacture of high performance, polyaryl ether polymers by reaction of bis(4,4 -chlorophenyl) sulfone with the disodium salts of dihydroxyphenols, eg, bisphenol A or 4,4 -sulfonylbisphenol (88). These and related reactions are made more economical by efficient recycling of DMSO (89). Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion in DMSO is a versatile and useful reaction for the synthesis of aromatic ethers and polyethers (90). 

Methane sulfonic acid, trifluoroacetic acid, hydrogen iodide, and other Brmnsted acids can faciUtate 3 -acetoxy displacement (87,173). Displacement yields can also be enhanced by the addition of inorganic salts such as potassium thiocyanate and potassium iodide (174). Because initial displacement of the acetoxy by the added salt does not appear to occur, the role of these added salts is not clear. Under nonaqueous conditions, boron trifluoride complexes of ethers, alcohols, and acids also faciUtate displacement (87,175). 

A.mina.tlon. Amination describes the introduction of amino groups into aromatic molecules by reaction of ammonia or an amine with suitably substituted halogeno, hydroxy, or sulfonated derivatives by nucleophilic displacement. Although reaction and operational conditions vary, the process always involves the heating of the appropriate precursor with excess aqueous ammonia or amine under pressure. 

There is a large variety of chloro or fluoro substituted heterocyclic rings which undergo X displacement by cell-0. Vinyl sulfones are usually generated under alkaline conditions from P-sulfatoethjisulfones,... 

The resins are made by batch processes employing Friedel-Crafts reactions or nucleophilic aromatic substitution. Udel resin and Radel R resin are produced by the nucleophilic displacement of chloride on 4,4 -dichlorodiphenyl sulfone by the potassium salts of bisphenol A and 4,4 -biphenol, respectively (97) ... 

Radel A 400 polyarylsulfone lesin is made from a piopiietaiy blend of bisplienols (believed to include hydioquinone) and dichloiodiphenyl sulfone. Victiex lesin is made by other displacement reactions. 

Phenazine reacts with benzenesulphinic acid in alcoholic hydrogen chloride to give 2-phenazinyl phenyl sulfone (26 Scheme 4), presumably by an intermediate 5,10-dihy-drophenazine this reaction is evidently a useful method of preparing 2-substituted phenazines, since the sulfone is readily displaced in substitution reactions. 

The preparation of esters can be classified into two main categories (1) carboxy-late activation with a good leaving group and (2) nucleophilic displacement of a caiboxylate on an alkyl halide or sulfonate. The latter approach is generally not suitable for the preparation of esters if the halide or tosylate is sterically hindered, but there has been some success with simple secondaiy halides and tosylates (ROTs, DMF, K2CO3, 69-93% yield). ... 

Racemization, however, does not alwiys accompany isotopic scrambling. In the case of 5ec-butyl 4-bromobenzenesulfonate, isotopic scrambling occurs in trifluoroethanol solution witiiout any racemization. Two mechanisms are possible. Scrambling may involve an intimate ion pair in which the sulfonate can rotate with respect to the caibocation without allowing migration to die other face of the caibocation. The alternative is a concerted mechanism, which avoids a caibocation intermediate but violates the prohibition of front-side displacement. ... 

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