Sulfonate ester derivative

Wc-Diols can also be deoxygenated indirectly, through sulfonate ester derivatives. For example, vic-dimesylates and Wc-ditosylates have been converted to alkenes by treatment, respectively, with naphthalene-sodium271 and with Nal in dimethylformamide.272 In another procedure, the diols are converted to bisdithiocarbonates (bis xanthates), which undergo... 

Among the different methods for the formation of C-C double bonds, the reductive elimination of (3-functionalized (mainly P-hydroxy or (3-carboxy) sulfones, is one of the most widely used ones in organic synthesis. The reductive elimination of (3-hydroxy sulfones and derivatives is the so-called Julia,94 or Julia-Lythgoe olefination reaction (Eq. 2). It usually involves a condensation between the anion of an alkyl sulfone and a carbonyl compound to afford a (3-hydroxy sulfone (Eq. 47). The metal alkoxide intermediate is typically transformed in situ into a carboxylic or sulfonic ester derivative, which is then reduced... 

The pinacol rearrangement of sulfonate esters derived from a-hydroxy acetals proceeds by way of intermediate oxonium species, which upon hydrolysis are transformed to the corresponding esters. Sulfonate 24, prepared in optically pure form by classical resolution of the diastereomer-ic mixture obtained from reaction of (-)-camphorsulfonyl chloride with the racemic naph-thenyl alcohol, undergoes thermal [1,2] rearrangement to yield the corresponding ester29. 

In contrast to the facile reaction of 1,2 3,4-di-0-isopropylidene-6-0-p-tolylsulfonyl-a-D-galactose with ethanethiolate anion, the same displacement reaction on 2,3 4,5-di-0-isopropylidene-l-0-p-tolylsulfonyl-/3-D-fructose, which also has a primary p-tolylsulfonyloxy group, proceeds more slowly, to give l-(S-ethyl-2,3 4,5-di-0-isopropylidene-l-thio-/3-D-fructose. This behavior parallels the reactivities of the two sulfonate ester derivatives with iodide ion. Inspection of models indicates that rear-side approach to C-1 in the D-fructose derivative is subject to considerably more steric hindrance than the approach to C-6 of the D-galactose derivative. 

The hydroxyl group of an alcohol can be converted to a good leaving group by conversion to a sulfonate ester derivative. The most common sulfonate esters used for this purpose are methanesulfonate esters ( mesylates ), y>-toluenesulfonate esters ( tosylates ), and trifluoromethanesulfonates ( triflates ). 

Alcohols are important for organic s)mthesis, especially in situations involving alkenes. The alcohol might be the desired product, or the OH group might be transformed into another functional group via halogenation, oxidation, or perhaps conversion to a sulfonic ester derivative. Formation of an alcohol from an alkene is particularly powerful because conditions can be chosen to produce either the Markovnikov or non-Markovnikov product from an unsym-metrical alkene. 

The history of the discovery of amino acids is closely related to advances ia analytical methods. Initially, quantitative and qualitative analysis depended exclusively upon crystallization from proteia hydrolysates. The quantitative precipitation of several basic amino acids including phosphotungstates, the separation of amino acid esters by vacuum distillation, and precipitation by sulfonic acid derivatives were developed successively duriag the last century. 

Sulfonate Esters. Sucrose sulfonates are valuable intermediates for the synthesis of epoxides and derivatives containing halogens, nitrogen, and sulfur. In addition, the sulfonation reaction has been used to determine the relative reactivity of the hydroxyl groups in sucrose. The general order of reactivity in sucrose toward the esterification reaction is OH-6 OH-6 > OH-1 > HO-2. 

Other methods for the preparation of cyclohexanecarboxaldehyde include the catalytic hydrogenation of 3-cyclohexene-1-carboxaldehyde, available from the Diels-Alder reaction of butadiene and acrolein, the reduction of cyclohexanecarbonyl chloride by lithium tri-tcrt-butoxy-aluminum hydride,the reduction of iV,A -dimethylcyclohexane-carboxamide with lithium diethoxyaluminum hydride, and the oxidation of the methane-sulfonate of cyclohexylmethanol with dimethyl sulfoxide. The hydrolysis, with simultaneous decarboxylation and rearrangement, of glycidic esters derived from cyclohexanone gives cyclohexanecarboxaldehyde. 

Another deviation from the normal displacement reaction of primary tosylates occurs in nucleoside derivatives (39, 81) where cyclonucleosides and anhydronucleosides are formed by participation of a nitrogen atom (as in purine nucleosides) and oxygen atom (as in pyrimidine nucleosides ), respectively. Iodonucleosides can result from these reactions only if these cyclic compounds are prone to attack by iodide ion. Several new examples of unexpected reactions during the solvolysis of sulfonate esters in sugar derivatives have been recorded in the past few years (2, 4,5,7,15,44,62,63,94). 

Metal halide salts other than sodium iodide have been used sparsely to prepare halodeoxy sugars from sulfonate esters. Lithium chloride (107) and lithium bromide (33) have found limited application. Potassium fluoride (dihydrate) in absolute methanol has been used (51, 52) to introduce fluorine atoms in terminal positions of various D-glucose derivatives. The reaction is conducted in sealed tube systems and requires... 

The use of tetra-n-butylammonium fluoride (54) in an aprotic solvent such as acetonitrile may be more advantageous. Foster and colleagues (19, 37) have effected an SN2 type of reaction using this reagent in the conversion of l,2 5,6-di-0-isopropylidene-3-0-p-tolylsulfonyl-D-allofura-nose into the C-3 epimeric fluorodeoxy derivative. Note that whereas potassium fluoride is ineffective in displacing secondary sulfonate esters in sugars, tetra-n-butylammonium fluoride is capable of effecting a displacement with Walden inversion even in a furanose drivative. 

Perhaps the earliest report of the replacement of a sulfonate ester attached to a secondary carbon atom in a sugar derivative was that of Helferich (53). Under quite drastic conditions (sodium iodide in acetone, 105°C., 72 hours, sealed system) the 4-mesylate derivative 9 was converted into a crystalline 4-deoxy-4-iodo sugar derivative 10 in 46% yield. Although the position of the iodine atom was established, the configuration at C-4 was not known. 

Trialkylboranes react rapidly and in high yields with a-halo ketones,a-halo esters, a-halo nitriles, and a-halo sulfonyl derivatives (sulfones, sulfonic esters, sulfonamides) in the presence of a base to give, respectively, alkylated ketones, esters, nitriles, and sulfonyl derivatives. Potassium tert-butoxide is often a suitable base, but potassium 2,6-di-tert-butylphenoxide at 0°C in THF gives better results in most cases, possibly because the large bulk of the two tert-buXy groups prevents the base from coordinating with the R3B. The trialkylboranes are prepared by treatment of 3 mol of an alkene with 1 mol of BH3 (15-16). With appropriate boranes, the R group transferred to a-halo ketones, nitriles, and esters can be vinylic, or (for a-halo ketones and esters) aryl. " °... 

Reaction of halo sulfonic acid esters with boranes 10-125 Alcoholysis of sulfonic acid derivatives 13-15 Vicarious substitution of aryl nitro compounds... 

This seeming unreactivity of vinyl halides in solvolytic processes and the lack of availability of more reactive precursors, such as sulfonate esters, until recently has discouraged early attempts at mechanistic investigations of vinyl cations generated by solvolyses. However, vinyl cations have been generated via vinyl diazonium ions derived from various precursors. 

Carboxylate anions derived from somewhat stronger acids, such as p-nilrobcnzoic acid and chloroacetic acid, seem to be particularly useful in this Mitsunobu inversion reaction.53 Inversion can also be carried out on sulfonate esters using cesium carboxy-lates and DMAP as a catalyst in toluene.54 The effect of the DMAP seems to involve complexation and solubilization of the cesium salts. 

As noted in the preceding section, one of the most general methods of synthesis of esters is by reaction of alcohols with an acyl chloride or other activated carboxylic acid derivative. Section 3.2.5 dealt with two other important methods, namely, reactions with diazoalkanes and reactions of carboxylate salts with alkyl halides or sulfonate esters. There is also the acid-catalyzed reaction of carboxylic acids with alcohols, which is called the Fischer esterification. 

The influence of other radicals in the stabilization of dihydroxytetrahy-drofuran rings should also be considered, as, for example, the p-toluene-sulfonic esters.41 When the compound LXI is hydrolyzed by acids, it gives the 2,5-anhydro derivative (LXII), whereas the compound LXIII gives D-glucitol. 

The common methods of esterification utilize an acid chloride or an acid anhydride as the reagent, but other acid derivatives often show different selectivities, and these are also considered here. In view of the extensive articles on sulfonic esters of carbohydrates,2 4... 

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