Esters, sulfonate solvolysis

Another example of solvolysis of a sulfonate has been described by Buchanan and coworkers 90 it occurs without acid, but utilizes a highly polarizable sulfonic ester group. Solvolysis of methyl 2-0-(p-nitrophenylsulfonyl)-a-D-glucopyranoside (84) in water in the presence of sodium acetate for 6 hours at 100° leads, after reduction of the reaction mixture by means of sodium borohydride, to a fraction identified as 2,5-anhydro-D-mannitol (85). This reaction, which... 

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)... 

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). 

C-6 with sulfuryl chloride. 181 Solvolysis of sulfonate esters,... 

Recently, anchimeric assistance was also reported in the solvolysis of dialkyl-j3-thiovinyl sulfonates (184). In particular, vinyl ester 221 reacts 3.8 X 10 times faster and vinyl ester 222, 4.2 x 10 times faster, respectively, than model compound 223 in 9 1 CH3N03 CH3 0H at 25°. The large anchimeric effects, 10 to 10, in the solvolysis of dialkyl- 3-thiovinyl sulfonates... 

Other examples of the solvolysis of sulfonates to give oxolanes have been reported. Thus, when 2,3-0-benzylidene-tri-0-(methylsulfonyl)-D-arabinitol, in a mixture of 9 M acetic acid and 10 M hydrochloric acid is heated for 30 minutes at 100°, it gives 2,5-anhydro-l,4-di-0-(methylsulfonyl)-D-arabinitol.88 Additional instances of the formation of internal anhydrides (not always well characterized) by acid hydrolysis of various sulfonic esters of alditols have been given by the same authors.88... 

The solvolysis of sulfonic esters, a much studied reaction, has not been applied in carbohydrate chemistry, presumably because most sugars are not stable enough to withstand the long heating required. Tosyl derivatives of inositols can, however, be solvolyzed in good yield. For example, 3-0-tosyl-feyo-inositol (5-0-tosyl-Zevo-inositol) (XLIV)—prepared from di-O-isopropylidene-fcvo-inositol (XXVIII) by tosylation and subsequent removal of the isopropylidene groups—affords aZZo-inositol when refluxed for... 

Experimental reactivity and mechanistic studies on the solvolysis of /3-sultams have shown that opening of the S-N bond produced a sulfonic acid or sulfonate ester and that there was no evidence of C-S fission. Alcoholysis of A-methyl-1,2-thiazetidine 1,1-dioxide 11 was investigated using ab initio calculations and density functional theory... 

A direct ionization, in which a leaving group attached to a carbon atom leaves with its pair of electrons, as in solvolysis reactions of alkyl halides (see p. 480) or sulfonate esters (see p. 522) ... 

Let us look at another example of solvolysis. A very commonly studied system is one in which the solvent is acetic acid (HOAc) and the substrates are alkyl esters of sulfonic acids ROTs, alkyl tosylates (alkyl p-toluenesulfonates) ROBs, alkyl... 

The primary approach was a development of the classical system investigated by Johnson [57], which involves initiation of carbocation formation following solvolysis of a sulfonate ester. In this scenario, once cyclization has occurred, the newly formed carbocation can be captured by either elimination or attack of a nucleophile. At an entry level, in an attempt to catalyze the cyclization of the acyclic sulfonate ester 35 two haptens, 36 and 37, were utilized in a bait-and-switch strategy (Scheme 8) [58]. HPLC assay revealed that four antibodies (4C6,16B5, 1C9, and 6H5) elicited to the N-oxide hapten 36 and one antibody, 87D7, elicited to the N-methylammonium hapten 37 were initiation catalysts, i.e., they catalyzed the solvolysis of the sulfonate ester bond of 35. A remarkable feature of antibody catalysis of this reaction is the narrow product distribution observed. Of all the possible products 38 to 42 inferred from the work of Johnson, only the cy-clized products 38 and 39 were detected, a testimony to the antibodies exquisite binding of a putative cyclic transition state as programmed by the haptens 36 and 37. 

A series of 0-labeled sulfonate esters was studied to determine the extent of scrambling that accompanies solvolysis. The rate of exchange was compared with that of solvolysis and the results are shown below. Discuss the variation in... 

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