Tosyl ates

Another quaternary anti arrhythmic agent is emilium tosyl-ate (65). It is synthesized simply by quaternization of... 

Correlation analysis of solvent effects on the heterolysis of p-methoxyneophyl tosyl-ate has been performed by using the Koppel-Palm and Kamlet-Taft equations. The reaction rate is satisfactorily described by the electrophilicity and polarity parameters of solvents, but a possible role for polarizability or nucleophilicity parameters was also examined. 

This interpretation has not been universally accepted, one reason being that the product ratios do not decline in like manner to the rate ratios. Another factor is that, even if the rate ratios are taken to indicate the existence of some participation of the electrons in the bond between C-1 and C-6 in the solvolysis of exo-2-norbornyl tosyl-ate, this is far removed from proving the existence of the symmetrical and hence fully delocalized ion at the transition state or as an intermediate in the reaction. Hence, if one concludes that the exo- and cndo-derivatives of the restricted systems are solvolysing to essentially unbridged or classical ions, the extent of bridging to be deduced from high exojendo rate ratios found with less restricted systems is unclear. 

These rates are some four orders of magnitude slower than tosyl-ate I and even the highly reactive benzyl tosylate is slower by a factor of 200 than I. It is also noteworthy that whereas tosylate I solvolyses substantially more rapidly than III, the solvolysis of the latter is also accelerated significantly. The extremely fast rate of solvolysis for compounds I and II demand that the N-nitroso group be involved in the reaction, which we postulated to take the following course. 

Reaction between halides or tosyl-ates and (Me3Si)2NNa... 

Fig. 46 Syntheses of multicyclic polyethers from TTSBI and oligo (ethylene glycol) tosyl-ates...

One way to increase the nucleofiigacity of halides is to introduce silver ion. Komblum reported that primary unactivated chlorides, bromides and iodides could be oxidized by prior conversion to the tosyl-ate with silver tosylate, followed by reaction in DMSO (Scheme 4). ... 

Tributylmethylphosphonium fluoride (BujMePF), which is prepared from tributylmetb-ylphosphonium bromide in two steps, " gives moderate yields of fluorides with primary tosyl-ates. With secondary tosylates the isolated yield of fluorinated products is low however, it has been reported that the optical purity of 2-fluorooctane obtained by this method is high. ... 

The acceleration of substitution reactions with azides using ultrasound techniques (Scheme 31) has not yet been investigated in detail. Activated primary halides react with trimethylsilyl azide (TMS-A) under particularly mild and absolutely neutral conditions (Scheme 31). Secondary and tertiary cyclic halides were treated with TMS-A/SnCU in CH2CI2 or CHCI3 to yield the corresponding azido compounds." Very impressive results with yields of about 90% were in this case reported in the adamantane and diamantane series." High solubility in organic solvents is also noticed with acetyl azide, which, prepared in situ, has also been used for azide syntheses. The scope of this reaction has still to be determined, however." Hassner noticed nearly quantitative yields of azides when alkyl halides (or tosyl-ates) were treated with polymeric quaternary ammonium azides. 

As expected on the basis of the epoxy halide results just discussed, die displacement of a primary tosyl-ate can be smoothly accomplished in the presence of an adjacent disubstituted epoxide,and this reaction has been utilized in syntheses of disparlure and of other insect pheromones. On the other hand, a recently reported reaction of a cyclic glucopyranose-derived epoxide with either Me2CuLi or MeMgCl-CuBr afforded in high yield the desired ring-opened product, leaving intact an exocyclic primary mesylate. 

Cope and Nealy5 epimcrized the czs-hydroxy ester (1) by conversion to the tosyl-ate (2),. S v2 displacement by tetraethylammonium acetate (with inversion), followed by alkaline hydrolysis of the ester. 

The synthetic utility of the chloral ene adducts has been extensively explored. Reaction with NaOR in ROH gives the a-alkoxy ester with inversion of configuration. Reaction of the corresponding tosyl-ate with sodium ethoxide in ethanol affords ethyl alka-2,4-dienoates (Scheme 9). 

Primary alkyl bromides are dehydrobrominated by er butoxide ion, but this same base displaces the tosyloxy group from the corresponding alkyl tosyl-ates. The difference must be related to the choice of hard and soft acceptors for the transition symbiosis clearly operates in the latter instances. 

To increase the steric demands and to remove the acidic NH group, N-tosyl-ated allylamine derivatives are converted to NTsBn, usingbenzylbromide-potas-sium carbonate-catalytic tetra-n-butylammonium iodide in acetone (Eq. 5.11), a reaction that is more convenient and affords the products in excellent yields. 

The X can be any good leaving group, such as I, Br, Cl, or OTs. In general, iodide and tosyl-ate are the best leaving groups. The alcohol in this case is phenol, which can be deproton-ated with sodium hydroxide (as we saw in Section 13.2). We therefore propose the following synthesis. 

Fluoroindolizines are easily available via cycloaddition of fluorinated vinyl tosyl-ates and pyridinium ylides [24], Using p-substituted pyridinium ylides both isomers (6 and 8) were formed with clear predominance of 8-isomers. One product with... 

Homoallenic participation has been measured using (214), which is believed to solvolyse through the same intermediate ion (Scheme 13) as the isomeric tosylate (215) on the basis of virtually identical product yields. The tosyl-ate (214) solvolyses approximately 40 times as fast as its saturated analogue... 

In light of your answer to Problem 11.50, which alkene, E or Z, would you expect from an E2 reaction on the tosylate of (2J, 3J )-3-phenyI-2-butanol Which alkene would result from E2 reaction on the (2S,3R) and (2S,35) tosyl-ates Explain. 

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