Alkyl sulfonates nucleophilic displacement

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). ... 

The main advantages of preparation of hydroxylamines through Af-alkylation of other hydroxylamines are versatility and predictable stereochemical outcome that allow the introduction of the hydroxyamino group at advanced stages of multistep syntheses. The use of nucleophilic displacement is however problematic for sterically hindered alkyl halides and sulfonates. Apart from several examples mentioned below, alkylation of hydroxylamines with tertiary alkyl halides does not take place. 

Problem 13.17 How does sulfonate ester formation from suifonyl chloride resemble nucleophilic displacements of alkyl halides "d... 

Reactions of organomagnesium compounds with dialkyl sulfates or alkyl sulfonates often give satisfactory yields of the products of displacement of sulfate or sulfonate. Side-reactions have been observed, but they can often be avoided for example, an excess of the sulfate or sulfonate should be used with Grignard reagents, as some is consumed by nucleophilic attack by halide ion [A]. The dialkyl sulfates are reactive, but hazardous. Toluenesulfonates (tosylates) are less reactive, but their reactions are catalysed by copper complexes the reactions of trifluoromethanesulfonates (triflates) are catalysed by nickel complexes. Reactions of Grignard reagents with secondary tosylates appear to follow an Sn2 mechanism, with inversion of configuration [43],... 

The preparation of fluorinated carbohydrates via nucleophilic displacement of the. sulfonate group of the corresponding sulfonates by fluoride is a well-known rcaction " however, potassium fluoride, which was used to prepare the first alkyl fluoride type of sugar derivative, has been progressively replaced by the alkylamine fluorides (.see Section 1.1.4.2.1.2.). The substitution of relatively unhindered primary mesylates or tosylates in cxocyclic positions of carbo-... 

Alkyl halides, alkyl sulfonates, and alkyl sulfates undergo nucleophilic displacement by aqueous sulfite to afford sulfonic acid salts under very mild conditions.This chemistry is traditionally referred to as... 

The sulfone is a versatile functional group comparable to the carbonyl functionality in its ability to activate molecules for further bond construction, the main difference between these two groups being that the sulfone is usually removed once the synthetic objective is achieved. The removal most commonly involves a reductive desulfonylation process with either replacement of the sulfone by hydrogen (Eq. 1), or a process that results in the formation of a carbon-carbon multiple bond when a P-functionalized sulfone, for example a (3-hydroxy or (3-alkoxy sulfone, is employed (Eq. 2). These types of reactions are the Julia-Lythgoe or Julia-Paris-Kocienski olefination processes. Alkylative desulfonylation (substitution of the sulfone by an alkyl group, Eq. 3), oxidative desulfonylation (Eq. 4), and substitution of the sulfone by a nucleophile (nucleophilic displacement, Eq. 5) are also known. Finally, p-eliminations (Eq. 6) or sulfur dioxide extrusion processes (Eqs. 7, 8 and 9) have become very popular for the... 

Sulfonate carbanions have been used less extensively than sulfone, sulfoxide, and sulfide carbanions. Sulfonates are good leaving groups and subject to nucleophilic displacement or elimination in the presence of the bases required to generate the carbanion. Cyclic sulfonates (sultones such as 330) have been alkylated via... 

These workers (10,11) have also utilized O2 to achieve an important synthetic objective in the prostaglandin field, namely the efficient conversion of 15-R (unnatural) prostaglandins into the 15- (natural) Isomers by nucleophilic displacement. These data all demonstrate the Sjj2 inversion character of 02 reacting with alkyl halides and sulfonate esters. 

The Williamson ether synthesis (Section 9-6) permits easy preparation of many alkoxybenzenes. The phenoxide ions obtained by deprotonation of phenols (Section 22-3) are good nucleophiles. They can displace the leaving groups from haloalkanes and alkyl sulfonates. 

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