Displacement toluenesulfonate

Higher perfluoroalkanesulfonates are slightly more reactive than triflates toward nucleophilic displacements. The rate constants for acetolysis of methyl nonafluorobutanesulfonate [6401 -03-2J, methyl trifluoromethanesulfonate [333-27-7] and methyl toluenesulfonate [80-48-8] are 1.49 x, ... 

The reaction of alcohols with acyl chlorides is analogous to their reaction with p-toluenesulfonyl chloride described earlier (Section 8.14 and Table 15.2). In those reactions, a p-toluenesulfonate ester was formed by displacement of chloride from the sulfonyl group by the oxygen of the alcohol. Carboxylic esters arise by displacement of chloride from a carbonyl group by the alcohol oxygen. 

Tokuyama and coworkers138,139 reported the displacement, with the thiocyanate ion, of the p-toluenesulfonate group in 2,3 4,6-di-0-isopropyl-idene-l-O-p-tolylsulfonyl-a-L-sorbofuranose (337) and 2,3-O-isopropyl-idene-l,6-di-0-p-tolylsulfonyl- -L-sorbofuranose (341) in liquid ammonia, as well as in N,N-dimethylformamide. Treatment of 337 with potassium... 

Another reason for the apparent inconsistencies in experimental data is that, depending on the nature and position of the substituent, steric and conjugative effects often outweigh polar influences. In order to study pure polar effects, Holtz and Stock have carried out rate studies of displacements by thiophenoxide ion on 4-Z-bicyclo-[2.2.2]-octylmethyl toluenesulfonate (Equation 4.17).37... 

A pentacyclic diterpene 1 called dictyoxetane contains a most unusual subunit, a 2,7-dioxatricyclo[4.2.1.03>8 ]nonane. During model studies designed to provide access to this key subunit the bicyclic ether 2 was synthesised in the hope that Sn displacement would generate the unsaturated tricyclic oxetane. There was no reaction when 2 was treated with base. Reaction with a catalytic amount of p-toluenesulfonic acid in DMF at 75°C for 24 hours resulted only in formation of 4-methylacetophenone. The hydroxy mesylate 2 is also reported to decompose to 4-methylacetophenone on storage. 

The reaction proceeds to form the alkyl p-toluenesulfonate as expected, but the chloride anion formed in this step subsequently acts as a nucleophile and displaces p-toluenesulfonate from RCH2OTs. 

The second step is a nucleophilic substitution in which benzoate ion displaces p-toluenesulfonate with inversion of configuration. 

M. Miljkovic, D. Miljkovic, A. Jokic, V. Andrejevic, and E. A. Davidson, Neighboring group participation in carbohydrate chemistry. 3. Neighboring group participation of the 6-hydroxyl group in a nucleophilic displacement of a 5-p-toluenesulfonate, J. Org. Chem., 37 (1972) 2536-2540. 

Roberts, J. D. Chambers, V. C. Small-ring compounds. VIII. Some nudeophilic displacement reactions of cydopropyl, cydobutyl, cyclopentyl and cydohexyl p-toluenesulfonates and halides./. Am. Chem. Soc. 1951, 73, 5034— 5040. 

The 1,2-diols formed by the asymmetric oxidation can be used as substrates in a wide variety of transformations. Conversion of the hydroxy groups to p-toluenesulfonates then allows nucleophilic displacement by azide at both centers with inversion of configuration (Scheme 9.22).161... 

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],... 

Reaction of cyclic sulfates or thionocarbonates, derived from 1,2-diols, with telluride results in stereospecific alkene formation <1995TL7209>. This is illustrated by the conversion of the cyclic sulfate OTitra-l,2-diphenyl-l,2-ethanediol 49 into fif-stilbene exclusively by Te, as shown in Equation (13). Treatment of the cyclic sulfate of 47-1,2-diphenyl-1,2-ethanediol with Te produces /ra r-stilbene exclusively. These results are accounted for by intermolecular Te Sn2 displacement followed by intramolecular Sn2 displacement to form the corresponding tellurirane. The tellurirane then thermally loses tellurium stereoselectively forming alkene. Cyclic sulfates need not be used dimethanesulfonates or di-/i-toluenesulfonates prepared from 1,2-diols also, stereospecifically, provide alkenes via telluriranes <1993CC923, 1996SL655>. 

A recent synthesis of the tricyclic secoiridoid ( )-sarracenin (98) relied on the Patemo-Biichi addition of acetaldehyde and cyclopentadiene as the initial step. Irradiation of cyclopentadiene and acetaldehyde provided a 5 1 mixture of bicyclic oxetanes (97) and (96) in 5-10% yield. Treatment of the crude photolysate with CSA and methanol followed by tosylation of the cmde product gave (99), which represents the toluenesulfonate ester derived from the major oxetane (97). The tosylate was displaced by the anion prepared from dimethyl 3-styrenylmalonate to afford the substituted malonate (100) in 84% yield (Scheme 10). Attempts to effect ring opening of the oxetane mixture were unsuccessful. Decarboxylation and demethylation gave the alcohol (102) which was subjected to ozonolysis and reductive work-up to afford ( )-sarracenin in 60% yield. The oxetane-based synthesis is noteworthy due to its brevity and use of a biosynthetically postulated trialdehyde equivalent. 

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