Alkyl sulfonates nucleophilic substitution

Alkyl sulfonate esters resemble alkyl halides m their ability to undergo ehmma tion and nucleophilic substitution... 

An advantage that sulfonate esters have over alkyl halides is that their prepara tion from alcohols does not involve any of the bonds to carbon The alcohol oxygen becomes the oxygen that connects the alkyl group to the sulfonyl group Thus the configuration of a sulfonate ester is exactly the same as that of the alcohol from which It was prepared If we wish to study the stereochemistry of nucleophilic substitution m an optically active substrate for example we know that a tosylate ester will have the same configuration and the same optical purity as the alcohol from which it was prepared... 

The mechanisms by which sulfonate esters undergo nucleophilic substitution are the same as those of alkyl halides Inversion of configuration is observed m 8 2 reac tions of alkyl sulfonates and predominant inversion accompanied by racemization m 8 1 processes... 

Sulfonate esters are especially useful substrates in nucleophilic substitution reactions used in synthesis. They have a high level of reactivity, and, unlike alkyl halides, they can be prepared from alcohols by reactions that do not directly involve bonds to the carbon atom imdeigoing substitution. The latter aspect is particularly important in cases in which the stereochemical and structural integrity of the reactant must be maintained. Sulfonate esters are usually prepared by reaction of an alcohol with a sulfonyl halide in the presence of pyridine ... 

Nucleophilic substitution reactions that occur imder conditions of amine diazotization often have significantly different stereochemisby, as compared with that in halide or sulfonate solvolysis. Diazotization generates an alkyl diazonium ion, which rapidly decomposes to a carbocation, molecular nitrogen, and water ... 

Alkyl sulfonates are frequently used as substrates for nucleophilic substitution reactions. 

Alkyl sulfonates provide an indirect method for carrying out nucleophilic substitution reactions on alcohols. 

Allkyl sulfonates undergo all the nucleophilic substitution reactions that alkyl halides do. 

Alkyl halides are often used as substrates instead of alcohols. In such cases the salt of the inorganic acid is usually used and the mechanism is nucleophilic substitution at the carbon atom. An important example is the treatment of alkyl halides with silver nitrate to form alkyl nitrates. This is used as a test for alkyl halides. In some cases there is competition from the central atom. Thus nitrite ion is an ambident nucleophile that can give nitrites or nitro compounds (see 0-60).731 Dialkyl or aryl alkyl ethers can be cleaved with anhydrous sulfonic acids.732... 

In the special case of nucleophilic substitution at a sulfonic ester RS020R where R is alkyl, R —O cleavage is much more likely than S—O cleavage because the OSOiR group is such a good leaving group (p. 353).1730 Many of these reactions have been considered previously (e.g., 0-4, 0-14, etc.), because they are nucleophilic substitutions at an alkyl carbon atom and not at a sulfur atom. However, when R is aryl, then the S—O bond is much more likely to cleave because of the very low tendency aryl substrates have for nucleophilic substitution.1731... 

The dicyclopentadienyl metal compounds undergo Friedel-Crafts alkylation and acylation, sulfonation, metalation, arylation, and formyla-tion in the case of ferrocene, dicyclopentadienyl ruthenium, and dicyclopentadienyl osmium, whereas the others are unstable to such reactions ( ). Competition experiments (128) gave the order of electrophilic reactivity as ferrocene > ruthenocene > osmocene and the reverse for nucleophilic substitution of the first two by n-butyl lithium. A similar rate sequence applies to the acid-catalysed cleavage of the cyclopentadienyl silicon bonds in trimethylsilylferrocene and related compounds (129), a process known to occur by electrophilic substitution for aryl-silicon bonds (130). 

Nucleophilic substitutions offer a more versatile means of access to alkyl halides than oxidative halogenations. The most common starting materials for this purpose are resin-bound alcohols, which can be converted into halides either directly or via the intermediate formation of sulfonates [23]. Polystyrene-bound halides can also be... 

A similar strategy in aqueous media has now been applied to the nucleophilic substitution of alkyl halides or tosylates using readily available alkali azides, thiocyanates or sulfinates under microwave irradiation. The approach afforded safe and efficient preparation of azides, thiocyanates and sulfones (Scheme 23) (Ju et al., personal communications). 

Fig. 2. Examples of nucleophilic substitution reactions performed in microemulsions. Scheme 1 synthesis of decyl sulfonate from decyl bromide and hydrogen sulfite. Scheme 2 synthesis of 2-hydroxyoctyl sulfonate from 1,2-epoxyoctane and hydrogen sulfite. Scheme 3 reaction of 4-nitrobenzylpyridine (NBP) with an alkyl halide (RX) followed by alkaline hydrolysis of the N-alkyl derivative (NBP-R+) formed. Scheme 4 a reaction involving displacement of the trinitrophenoxide ion by bromide...

The 2-cyano-cycloalkanones are easy to prepare but only in moderate yields [18]. The introductions of nitro- [6] and sulfone- [5] [116] [117] groups are simpler than the cyano group, and the yields are better. Sulfone and cyano compounds are most suitable for the introduction of the side chain. Beside the Michael reaction [16] [97], and the Pd(O) catalyzed addition [15], and the reactions with alkyl halides [16] [17] proceed in good yields. In contrast to other compounds, 2-nitroketones generally do not undergo nucleophilic substitution with non-activated alkyl halides. However, Michael addition products [2], as well as products synthesized by Pd(O) catalyzed alkylation [118], are well known derivatives of 2-nitrocycloalkanones. 

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