Sulfonates brosylate

The compound 2-octyl brosylate was labeled at the sulfone oxygen with 0 and solvolyzed. The unreacted brosylate recovered at various stages of solvolysis had the 0 considerably, though not completely, scrambled ... 

Although halides are common leaving groups in nucleophilic substitution for synthetic purposes, it is often more convenient to use alcohols. Since OH does not leave from ordinary alcohols, it must be converted to a group that does leave. One way is protonation, mentioned above. Another is conversion to a reactive ester, most commonly a sulfonic ester. The sulfonic ester groups tosylate, brosylate, nosylate, and mesylate are better leaving groups than... 

Sulfonic esters are most frequently prepared by treatment of the corresponding halides with alcohols in the presence of a base. The method is much used for the conversion of alcohols to tosylates, brosylates, and similar sulfonic esters. Both R and R may be alkyl or aryl. The base is often pyridine, which functions as a nucleophilic catalyst, as in the similar alcoholysis of carboxylic acyl halides (10-21). Primary alcohols react the most rapidly, and it is often possible to sulfonate selectively a primary OH group in a molecule that also contains secondary or tertiary OH groups. The reaction with sulfonamides has been much less frequently used and is limited to N,N-disubstituted sulfonamides that is, R" may not be hydrogen. However, within these limits it is a useful reaction. The nucleophile in this case is actually R 0 . However, R" may be hydrogen (as well as alkyl) if the nucleophile is a phenol, so that the product is RS020Ar. Acidic catalysts are used in this case. Sulfonic acids have been converted directly to sulfonates by treatment with triethyl or trimethyl orthoformate HC(OR)3, without catalyst or solvent and with a trialkyl phosphite P(OR)3. ... 

It is evident from the foregoing sections that simple alkylvinyl halides do not react via an Sn 1 mechanism, if at all, even under extreme solvolytic conditions (146,149). More reactive leaving groups, such as arylsulfonates, were clearly needed to investigate the possible solvolytic behavior of simple alkylvinyl systems, but the preparation of vinyl sulfonates until recently was unknown. Peterson and Indelicato (154) were the first to report the preparation of vinyl arylsulfonates via reaction of the appropriate disulfonate with potassium t-butoxide in refluxing f-butanol. They prepared and investigated the solvolysis of 1-cyclohexenyl tosylate 169 and c/s-2-buten-2-yl tosylate 170 and the corresponding p-bromobenzenesulfonates (brosylates). Reaction... 

The solvolysis of optically active exo-2-norbornyl brosylate (74) affords completely racemic products. The rate of racemization exceeds the rate of solvolysis, indicating return from an achiral ion pair89). Products of return to isomeric cations were isolated from the solvolysis of many substituted norbornyl sulfonates some... 

The most frequently synthesized and used cellulose sulfonates are the p-toluenesulfonates (tosylates), methanesulfo-nates (mesylates), p-bromobenzenesulfonates (brosylates), and ttifluoromethanesulfonates (Inflates). The synthesis of sulfonates through simple esterification of the -OH groups of cellulose with the corresponding sulfonic acid chlorides or anhydride is a way to attach nucleofuge groups to... 

Brown s approach was to show that the properties ascribed to the nonclassical ion could be duplicated in systems involving classical carbocations. Since the rate enhancement of solvolysis of the exo isomer was an important part of the argument for (7-bond participation, he also analyzed the relative reactivities of various systems. He argued that the cxo-norbomyl system should be compared to the cyclopentyl system rather than to cyclohexyl brosylate. The torsional relationship of the leaving group and adjacent substituents is eclipsed in norbomyl sulfonates, and strain is relieved on ionization. Cyclohexyl brosylate, in contrast, is completely staggered in the ground state, and so no strain relief accompanies ionization. In the cyclopentyl... 

The reaction of 8-hydroxy acids with p-bromobenzenesulfonyl chloride in the presence of a tertiary amine gives /3-lactones (eq 5). Brosylate esters of oximes have been manipulated in the Beckmann rearrangement of erythromycin derivatives as an alternative to both 4-methylbenzenesulfonate esters and benzene-sulfonate esters. 

Schuerch has synthesized 0-benzyl-protected mannosyl brosylate, tosylate, tre-sylate, and triflate derivatives 23 from the corresponding chloride 22 and the respective silver sulfonate [96]. On exposure to MeOH, the sulfonates 23 give a nearly 1 1 mixture of methyl a- and P-mannosides 24 (Scheme 8). 

These effects, determined with tertiary chlorides, unquestionably refer to 8n1 reactions so also do Lewis and Boozer s effects on acetolysis and formolysis—-if we can rely on the constancy of the effect of a-deuteration (Table VIII). The /3-effects then suggest that formolysis of the secondary bromide and solvolysis in aqueous ethanol of the tosylate are also SnI—or nearly so, unless bimolecular displacement reactions are also subject to similar isotope effects. Shiner (117) had however already shown that this was not so, since deuteration in the two methyl groups of isopropyl bromide did not lead to an experimentally significant effect on the displacement reaction with ethoxide ion in ethanol. It is thus also reasonable to interpret the very small effect (AAF" = 6 cal.) cited by Lewis (74f) for acetolysis of ethyl-2d8 brosylate as evidence that acetolysis of primary sulfonate esters is borderline if not Sn2. This conclusion, already suggested by the abnormally low a-effect for unassisted acetolysis of phenylethyl tosylate [Table VIII and text of Sec. VA, 2(b) 1 is supported by a similarly... 

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