Alkanesulfonates formation

TABLE 19 Enthalpies of Micelle Formation for Alkanesulfonates in Water... 

Frequently substantially more than catalytic amounts of a Lewis acid metal halide are required to effect Friedel-Crafts alkylation. This is due partly to complex formation between the metal halide and the reagents or products, especially if they contain oxygen or other donor atoms. Another reason is the formation of red oils. Red oils consist of protonated (alkylated) aromatics (i.e., arenium ions) containing metal halides in the counterions or complexed with olefin oligomers. This considerable drawback, however, can be eliminated when using solid acids such as clays,97 98 zeolites (H-ZSM-5),99,100 acidic cation-exchange resins, and perfluoro-alkanesulfonic acid resins (Nafion-H).101-104... 

The formation of the sultone (160) probably involves addition of the complex across the alkene double bond, a 1,2-hydride shift and an intramolecular nucleophilic substitution reaction. The sultone (161) is formed by addition of sulfur trioxide to give the unstable p-sultone which rearranges to the more stable y-isomer (161). Another useful route to sultones is by metallation of alkanesulfonate esters for example, butane-1,3-dimethylsulfonate (162), prepared from butanel,3-diol, yields the 8-sultone, namely 6-methyl-l,2-oxathiin-2,2-dioxide (163) (Scheme 67). 

Smaller organic anions Amino acids, alkane caiiwxylic acids (formate, acetate, propionate, butyrate), chloro carboxylic acids (chloroacetate, dichloroacetate), hydroxy acids (hydroxyacetate, lactate, tartrate, citrate), glycolate, gluconate, pyruvate, dicarboxylic acids (oxalate, malonate, succinate, glutarate, fumarate, maleate), alkanesulfonic acids (methanesulfonate, ethanesulfonate). 

Virtually all of the vast number of methanesulfonate, or mesylate , esters prepared to facilitate elimination or substitution of a hydroxyl function have been prepared from sulfene the standard procedure using methanesulfonyl chloride and triethylamine in dichloromethane has been described by Crossland and Servis138. To be sure, sulfene intermediacy is not required for alkanesulfonate ester formation the reaction, as has been noted (in Section IV.A.2), will proceed without base promotion via the direct displacement route, but it is usually sufficiently sluggish, however, that the further reaction of the ester with the alcohol competes with ester formation139. This makes the procedure a poor one for most practical purposes, although we recently encountered an instance, namely the preparation of neopentyl 2-chloroethanesulfonate87, in which the direct reaction of the alcohol and sulfonyl chloride without base was the method of choice this arose because (a) the product is stable and (b) 2-chloroethanesulfonyl chloride does not yield the corresponding sulfene with tertiary amines (Section IV.A.2). 

The alkanesulfonic acids themselves are not suitable starting materials for electrochemical fluorination because the yields of perfluoroalkanesulfonic acids obtained from the free acids are much lower compared to the alkanesulfonyl fluorides and chlorides. Another major disadvantage of this approach is the formation of water, which may result in the formation of explosive oxygen difluoride (OF2). 

There have been further reports on the rate enhancement observed when the normal complex [Ni(pada)] is formed in the presence of micelles. These can be very considerable but it has been found that sodium alkanesulfonates are about 25% less effective in this respect than the alkyl sulfates. The effect of various anionic polyelectrolytes on this reaction has also been studied it ranges from an acceleration of about two orders of magnitude in the case of poly(styrene sulfonate) to a retardation by about one order of magnitude for polyphosphate and seems to be dependent on the state of hydration of the Ni ion when condensed in the polyelectrolyte domains. Polyphosphate exerts a similar retardation on the formation of [CoCpada)] " and the effect is attributed to the complete replacement of the coordinating water by the polyelectrolyte. Activation... 

Hicks, J.R., Reinsborough, V.C. Rate enhancement of the nickel(II)-PADA complex formation in sodium alkanesulfonate micellar solutions. Ausf. J. Chem. 1982, 35(1), 15-19. 

---