2- Octyl tosylate

A comparison of displacements on (/ )-2-octyl tosylate, chloride and bromide by PhsCLi, Ph3SiLi, PJ GeLi and Pt SnLi is summarized in Table 640. In each case, the Sjv2 product is formed with inversion. The basicity of the triphenylmethyl anion caused... 

A detailed study of the formation of n-octyl ethers under solidrliquid two-phase conditions in the absence of an added solvent has been reported [10], Potassium alkoxides tend to produce higher yields of the ethers than do the corresponding sodium derivatives, but octene is the major product in the reaction of 1-bromooctane with potassium t-butoxide. High temperatures also tend to promote the preferential formation of octene and slightly higher yields of the ethers are obtained using n-octyl tosylate in preference to n-octyl bromide. p-Fluorinated acetals have been prepared either under basic catalytic liquidrliquid or solidrliquid conditions from the fluori-nated alcohol and dichloromethane [11] with displacement of the fluorine atoms. 

Cesium fluoride has been used to displace halogens, sulfonate groups and nitro groups among others, with fluorine. 1-Bromooctane (1), ethyl bromoacetate (2), benzyl bromide (3) and octyl tosylate (4) have been converted to the respective fluorides 5-7 by treatment with cesium fluoride in the presence of 10% tetraalkylammonium salt (Bu4NBr or Aliquat 336) in the absence of solvent.166... 

Figure 15. Correlation of solvolytic rate constants for bicydo[2,2,2] octyl tosylate [49] at 25° and YqTs (data from Morten, 1975).

Other evidence to support the selection of 2-adamantyl tosylate as model compound has been discussed in Section 2 (p. 8), and the main conclusion can be summarized as follows. Independent evidence and the results in Fig. 15 firmly establish that nucleophilic solvent assistance cannot be appreciable for solvolyses of 2-adamantyl tosylate, since its response to solvents of widely varying nucleophilicities is almost exactly the same as 1-bicyclo [2,2,2] octyl tosylate [49] for which rearside attack is impossible if solvolyses of 2-adamantyl tosylate are anchimerically assisted, the extent of anchimeric assistance does not appear to be dependent on solvent (cf. Pritt and Whiting, 1975). In addition to these conclusions, the results in Fig. 14 suggest that internal return from intermediate contact ion pairs does not occur to a detectable extent for solvolyses of 2-adamantyl tosylate (see also Bentley and Schleyer, 1976). 

Bicyclooctyl Cations. Solvolyses of endo-2-bicyclo[3.2.1]octyl tosylate (73)55S and 4-cycloheptenylcarbinyl brosylate (4< 7)377 555 give similar product mixtures consisting primarily of endo-2-bicyclo [3.2.1] octanol or its acetate (819)... 

Solvolyses of 2-bicyclo [2.2.2] octyl tosylate (814) and exo-2-bicydo [3.2.1 ] octyl tosylate (815) give mixtures of (277) and (278) having the same composition (Table 18)555. These results are compatible with the view that (814) and (815) give rise to the same bridged ion (818). The products derived from optically active tosyla-tes, however, are partially racemic555 In all cases the [2.2.2] isomer (277) is less... 

Hydrogen shifts do occur in the solvolysis of exo- and enJo-6-bicyclo [3.2.1] octyl tosylates, (820) and (822)ss. Both substrates produce exo-6-bicyclo [3.2.1 ]... 

For instance, addition of "BuMgCl to a mixture of styrene, octyl tosylate, and a catalytic amount of zirconocene dicliloride in THF at 20°C gave 2-phenyldecane in 62% yield. In this reaction octane was formed by the reduction of octyl tosylate as a byproduct in trace amounts (<3% based on octyl tosylate) along with dodecane (< 1%) probably formed by direct reaction of octyl tosylate with BuMgCl. 

Separation of Nucleophilic and Electrophilic Contributions to Solvation Effects. The discussion on the appropriate choice of m value for the N0Ts scale (equation 7) is part of a more general problem of dissecting the nucleophilic contributions (corresponding to the IN term in equation 5) and electrophilic contributions (included in the mY term in equation 5) to solvent effects. When a substrate reacts by a nucleophilically solvent assisted pathway, m decreases and l increases, often in a uniform manner (equation 12). Schadt et al. proposed (3) that an increase in nucleophilic assistance (increase in l) caused delocalization of positive charge, which led to a decrease in m. All of the deviations from the rates expected for SN1 (kc) reactivity were attributed to nucleophilic solvent assistance (3) Schadt et al. (3) assumed that m values for kc processes would be the same as for 2-adamantyl (II), and more recent data for 1-adamantyl (I), 1-adamantylmethylcarbinyl, and 1-bicyclo[2.2.2]octyl tosylates support this assumption (4, 53). 

Comparison of the calculated nucleophilic accelerations of 9, 17, and 106 to the degree of inversion (72, 74, and 87%, respectively) for Vla-c shows that even though the kinetic effects of solvent assistance are significant, this fact does not lead to the complete inversion characteristic of the SN2 reaction as found in acetolysis of 2-octyl tosylate (45). The best description of the first intermediate in the solvolysis of Vla-c would thus appear to be the solvated ion pair shown in Scheme II. In this species, the solvent is involved in nucleophilic solvation of the central carbon as well as the remainder of the carbocation and also participates in electrophilic solvation of the anion. Numerous solvent molecules are involved, and no strong interaction of a single nucleophilic solvent molecule at the central carbon leading to exclusive inversion occurs. 

The acetolysis of the exo-8-anti-tricyclo[3,2,l,0 ]octyl tosylate 554 proceeds three times slower than that of the nonreactive 7-norbomyl tosylate 4 In compound 554 the p-like orbitals of and involved in the formation of the C —bond are remote from the 8-position where the cation centre arises but the face participation of the cyclopropane fragment seem to be insignificant. At the same time the endo isomer 555 solvolyzes 10 times as fast as the exo-epimer 554 in this case the above-mentioned orbitals are directed to the 8-position (edge participation). The hydrolysis of this tosylate in 70 % aqueous acetone results in an alcohol mixture containing 99.9% of a rearranged alcohol — endo-3-tricyclo[5,l,-0,0 ]octanol 556 — and 0.1 % of alcohol 557 which retains the parent skeleton and configuration. 

Another convenient procedure for the reductive removal of the mesylate or tosylate group is through reaction with a Nal/Zn system The iodide intermediate which is formed in the reaction is reduced to the alkane with zinc powder. Following this procedure 2-octyl tosylate could be reduced to n-octane in high yield (equation... 

The method by which the stereochemical course of a nucleophilic substitution reaction is determined can be illustrated for the case of 2-octyl tosylate ... 

Similarly, the stereochemistry of ethanolysis of 2-octyl tosylate was determined to be clean inversion of configuration ... 

Entry 4 presents an early result on the gross stereochemistry of acetolysis of 2-octyl tosylate. We have seen earlier that after correction for racemization of the substrate and the product and addition of acetic acid to octenes under the reaction conditions, the displacement step occurs stereospecifically with inversion. The results cited in entry 5 are important and illustrate the importance of solvation of the ion-pair intermediates in nucleophilic substitution reactions of secondary substrates. In aqueous dioxane, the ion-pair intermediate may be solvated by water molecules or by dioxane. Inverted product results from solvation by water, but solvation by dioxane cannot collapse to a stable product. Subsequent solvation steps can lead to symmetrical solvation or attack by water from the front side, displacing dioxane. The observed result is the formation of partially racemic 2-octanol ... 

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