Alkyl mesylate

In contrast to phosphorus esters, sulfur esters are usually cleaved at the carbon-oxygen bond with carbon-fluorine bond formation Cleavage of esteri nf methanesulfonic acid, p-toluenesidfonic acid, and especially trifluoromethane-sulfonic acid (tnflic acid) by fluoride ion is the most widely used method for the conversion of hydroxy compounds to fluoro derivatives Potassium fluoride, triethylamine trihydrofluoride, and tetrabutylammonium fluoride are common sources of the fluoride ion For the cleavage of a variety of alkyl mesylates and tosylates with potassium fluoride, polyethylene glycol 400 is a solvent of choice, the yields are limited by solvolysis of the leaving group by the solvent, but this phenomenon is controlled by bulky substituents, either in the sulfonic acid part or in the alcohol part of the ester [42] (equation 29)... 

Wittig reactions can also be performed with support-bound phosphorus ylides. Polystyrene-bound alkylphosphonium salts have been prepared from the corresponding alkyl mesylates or halides and trialkyl- or triarylphosphines (Figure 5.8 [60,80]). Because polystyrene is a hydrophobic support, salt formation does not proceed smoothly and quaternization of phosphines generally requires forcing conditions. The... 

Substrates susceptible to Sn 1 attack and those bearing leaving groups other than halides have also been employed in the Michaelis-Arbuzov reaction, for example, dialkyl sulfates, alkyl mesylates, alkyl tosylates, quaternary ammonium species, activated acetates as have other electrophiles, for example, alkyl fluoroborates, lactones, lactams, aziridines, sulfones, iminium cations, and orf/io-quinonoids.6,13-15,18... 

The process is accelerated by the presence of powerful ion-solvating medium and metal ions such as Ag+ ions or Lewis acid. In place of alkyl halides, alkyl tosylates and alkyl mesylates can also be used. 

Alkyl mesylates undergo alkylation reaction with benzene rings in the presence of Sc(OTf)3. " Allylic acetates undergo alkylation with Mo(CO)g and allylic chlorides react in the presence of ZnCl2/Si02. " Montmorillonite clay (KIO) is an effective medium for alkylation reactions.Nafion-H, a super acidic perfluori-nated resin sulfonic acid, is a very good catalyst for gas phase alkylations with alkyl halides, alcohols,or alkenes. 

The reaction with ammonia probably starts with the primary alkyl mesylate and the second step is j corey and group in Tetrahedron then intramolecular. It is also stereospecific - the Sn2 displacement must occur with inversion and, Lett., 1979, 671. fortunately, the amine is already on the bottom face. 

Of the activated alcohols described in Section 1.1.2.S.1, alkyl sulfonates ate convenient alkylating re-agents because they can be readily prepared and handled. The correct choice of sulfate-alcoholate combination is often crucial for successful ether synthesis. Thus, for the preparation of cholesteryl ethers from the tosyl derivative of cholesterol and alkoxides, the reaction must be carried out at 110 °C for 2.S h in a sealed tube. Alternatively, the sodium salt of cholesterol can be reacted with an alkyl mesylate at 80 °C for 1 h in DMF to give the corresponding ether in 62-68% yield. ... 

The above-mentioned reactions for the introduction of bromine always involve an activation of the alcohol as the first step. In some cases it can be useful to isolate the activated intermediate. The reactions of alkyl mesylates or tosylates with MgBr2 give alkyl bromides under mild conditions with good yields (equation 20) Neopentyl tosylate with LiBr in HMPA gives neopentyl bromide in 67% yield (equation 21). Complete inversion with little or no rearrangement is observed in this difficult case. 

During the endgame of the total synthesis of the stemona alkaloid (-)-stenine, Y. Morimoto and co-workers utilized the Finkelstein reaction to prepare a primary alkyl iodide from a primary alkyl mesylate. The mesylate was prepared from the corresponding primary alcohol with MsCI/EtsN. The resulting primary alkyl iodide was used in the subsequent intramolecular N-alkylation to construct the final perhydroazepine C-ring of the natural product. 

Substitution. CsF is an excellent fluoride ion source for converting alkyl mesylates to RF, especially in the presence of the imidazolium mesylate 1. The effect, due to hydrogen bonding to the tertiary alcohol to render the fluoride ion more nucleophilic but less basic (so as to minimize elinination [H-OMs]), is also manifested in a polymer-linked 1, and a combination of r-AmOH and a polymer-supported ionic liquid. ... 

David, J. Snodin, Residues of genotoxic alkyl mesylates in mesylate salt drug substances real or imaginary problems Regulatory Toxicology and Pharmacology, 45 (1), 79-90, 2006. www.emea.europa.eu/htms/human/swp/swpHn.htm CPMP/SWP/5199/02. 

Friedel-Crafts alkylation. Secondary alkyl mesylates are adequate alkyl donors in this reaction." Both Sc(OTf)3 and TfOH can be used as the catalyst. It has also been reported that Sc(OTf js immobilized in ionic liquid forms a recyclable system for arene alkylation with alkenes. ... 

Rather than starting from 1-methylimidazole, imidazole can be converted to 1-alkylimidazole following deprotonation with a strong base. Quaternization leads to the formation of imidazolium cations that can bear a variety of alkyl substituents. Instead of halide derivatives, alkyl mesylate, tosylate or triflate can also be used, resulting in the direct formation of ionic liquids with these corresponding anions (Scheme A one-step preparation of hydrophobic... 

Inversion of Chiral Alcohols. One of the most common applications for cesium acetate is its use in the inversion of the stereochemistry of secondary alcohols that have been converted into better leaving groups. Once the acetate is substituted via a direct SN2-fike displacement, it can then be easily converted back to the alcohol. Some attribute the enhanced nucleophilicity of cesium acetate to a cesium effect. Previously, cesium propionate had been used with alkyl mesylates. The use of this reagent generally resulted in good yields and was preferred to other methods, but it could lead to complicated interpretation of resulting H NMR spectra, whereas an acetate product could be more easily carried forward into further synthetic modification. 

Nucleophilic Substitutions.—Many of the nucleophilic substitutions covered by equation (1) can be catalysed as effectively in liquid-liquid two-phase systems by crown and cryptand compounds as by quaternary ions. Alkyl substitution on the basic crown skeleton of (28), as in (31), was found to increase the efficiency of catalysis for the conversion of alkyl mesylates to halides, presumably by ensuring partitioning of the crown-salt complex between the phases. A similar observation has been made using alkyl-substituted crown (32) and aza-crown compounds (33) as catalysts in two-phase reactions, for example between iodide, cyanide or thiocyanate aniohs and an alkyl bromide. Alkyl substitution in the macrobicyclic cryptands (34) has the same effect on Sn processes, and in all the above cases systems can be devised with catalytic efficiency comparable to or greater than that achieved by quaternary ion PTC. 

SCHEME 7.31 Using alkyl mesylates in Finkelstein reactions [54]. 

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