Isopropyl tosylate

Solvolysis rates of isopropyl tosylate and 2-adamantyl tosylate (28, p. 243) in 80 percent ethanol are measured with and without added azide. Define rate enhancement, R.E., as the ratio of rate with azide to rate without, and designate by /bn3 the fraction of alkyl azide in the product. Explain the significance of the fact that the isopropyl results fit the equation... 

Ethyl tosylate and isopropyl tosylate were evaluated as precursors of />-tolue-nesulfonic acid [38]. It was presumed that these esters would decompose at elevated temperatures as shown in Scheme 4.4. 

The residual styrene contents in PS prepared by the polymerization of styrene in the presence of ethyl tosylate (1 mol%) initially increased upon heating to 260 °C but then decreased with time (Table 4.3). After 2h, residual styrene levels were reduced to an undetectable level. Isopropyl tosylate is much... 

Fig. 9. Absence of a free-energy correlation for the solvolysis of isopropyl tosylate in representative solvents. I Reproduced from Brown, H. C. The nonclassical ion problem. New York Plenum Press 1977.1...

The parameter Y is defined by the solvolysis of 2-adamantyl tosylate and Figure 11 illustrates the fit to Equation (32) for the solvolysis of isopropyl tosylate. The additional term introduces a better correlation and indicates that the solvolysis has substantial nucleophilic assistance (/ = 0.4) in the transition structure as would be expected. 

Figure 11 Extended Grunwald-Winstein plot for the solvolysis of isopropyl tosylate , plot of the data against , improved plot when bilinear equation is...

Finally, strong solvation of the carbenium ion intermediate also causes a marked reduction in secondary (5-deuterium KIE.84 For example, the (5-deuterium KIE in the solvolysis of isopropyl tosylate is reduced from 1.13/(5-D in trifluoroethanol, which does not solvate the developing carbenium ion strongly, to 1.08/ p-D in water where the carbenium ion is strongly solvated. Again, hyperconjugation is reduced because the solvent stabilizes the developing carbenium ion in the transition state. 

The value of m from the Winstein-Grunwald equation (for 2-endo-tosylate 0.69, i.e. between 2-adamantyl tosylate, 0.91, and isopropyl tosylate, m = 0.44)also points to some participation of the solvent. Finally, as shown by Nordlander et al. kjikj, = 30 for the solvolysis of 2-endo-norbornyl tosylate. If this ester was solvolyzed with considerable steric hindrance to ionization the solvent participation would be unusually great while the ratio observed coincides with that for trans-2-methylcyclopentyl tosylate (kjikj = 30). 

Tipson devoted most of his years in Levene s laboratory accomplishing seminal work on the components of nucleic acids. To determine the ring forms of the ribose component of the ribonucleosides he applied Haworth s methylation technique and established the furanoid structure for the sugar in adenosine, guanosine, uridine, and thymidine. He showed that formation of a monotrityl ether is not a reliable proof for the presence of a primary alcohol group in a nucleoside, whereas a tosyl ester that is readily displaced by iodide affords clear evidence that the ester is at the 5-position of the pentofuranose. Acetonation of ribonucleosides was shown to give the 2, 3 -C -isopropyl-idene derivatives, which were to become extensively used in nucleoside and nucleotide chemistry, and were utilized by Tipson in the first chemical preparation of a ribonucleotide, inosinic acid. 

Potassium cyanide has been caused to react with salts and esters of sulfonic acids to give nitriles. Thus, an intimate mixture of finely powdered potassium cyanide with the compound may be fused 422 this method was successfully applied428 to tetrahydrofurfuryl p-toluenesul-fonate and methanesulfonate, but failed with l,2 3,4-di-0-isopropylidene-6-O-tosyl-D-galactose. Another method, consisting of treatment of the ester with a stirred, boiling, saturated, aqueous solution of potassium cyanide gave885 a 70 to 83% yield of nitrile with primary p-toluenesul-fonates (ethyl, n-butyl, and n-octyl) and a 43% yield with a secondary p-toluenesulfonate (isopropyl). Similar methods had been applied earlier98 841 to such simple esters, but have not apparently found use with sulfonic esters of carbohydrates. 

In contrast to typical mono- or acyclic substrates (e. g.,isopropyl), 2-adaman-tyl derivatives are also found to be insensitive to changes in solvent nucleophilicity. A variety of criteria, summarized in Table 13, establish this point. In all cases, the behavior of 2-adamantyl tosylate is comparable to that observed for its tertiary isomer but quite unlike that observed for the isopropyl derivative. Significant nucleophilic solvent participation is indicated in the solvolysis reactions of the isopropyl system. The 2-adamantyl system, on the other hand, appears to be a unique case of limiting solvolysis in a secondary substrate 296). The 2-adamantyl/ isopropyl ratios in various solvents therefore provide a measure of the minimum rate enhancement due to nucleophilic solvent assistance in the isopropyl system 297). 

A solution of 9.5 g of tosyl chloride in 125 ml of pyridine was added to a mixture of 6.6 g of the product of step 7 and 66 ml of pyridine and the mixture was stirred at 20°C for 17 hours and was then poured into methylene chloride. The mixture was washed with aqueous saturated sodium bicarbonate solution, dried and evaporated to dryness. The residue was chromatographed over silica gel and was eluted with a 95-5 methylene chloride-methanol mixture to obtain 7.7 g of [6aRS-(6aa,9p,10aP)]-4,6,6a,8,9,10a-hexahydro-7-methyl-7H-indolo[3,4-g,h][l,4]benzoxazine-9-p-toluenesulfonate-methanol which after crystallization from an isopropyl ether-methylene chloride mixture melted at 180°C. 

Polymers with pendant carbodiimide groups 27 are also synthesized from crossUnked polystyrene. In this synthetic route crossUnked polystyrene beads are chloromethylated and converted to the amines. Reaction with isopropyl isocyanate gives the corresponding ureas, which are treated with tosyl chloride and triethylamine to produce the crossUnked polycarbodiimides. This polymer is used in the polymer supported Moffatt oxidation of alcohols into aldehydes or ketones using benzene/DMSO. ... 

If a C-substituted derivative of TOSMIC is used in the reaction, the product is a 1,4,5-trisubstitutcd imidazole. Such substituted isocyanidcs can be made either by dehydration of the iV-(a-tosylalkyl)formamide, or by alkylation of an appropriate isocyanide followed by reaction with tosyl fluoride. It is also possible to alkylate TOSMIC directly using phase transfer conditions 13], Such alkylations work best with primary alkyl halides (75-95%), with the isopropyl (40%), allyl (75%) and benzyl (80%) derivatives proving quite accessible. 

Replacement of the chloro substituent by methoxide has been observed in the following pyrazines 2-chloro-3-methoxycarbonyl (at <5°) (867) 2-chloro-6-methoxycarbonyl (870) 2-chloro-3-methoxycarbonyl-5,6-diphenyl (371, 837) 2-carboxy-6-chloro (869, 871) 2-carbamoyl-5( )-chloro (839) 2-carbamoyl-6-chloro (805, 839) 2-chloro-6-(4 -morpholinocarbonyl) (870) 2-chloro-3-cyano (810, 811) 5-chloro-3-cyano-2-methoxy (reflux 14h) (881) 2-chloro-5-methoxy-3,6-dimethyl (844) 2-chloro-5-isopropyl-6-methoxy-3-methyl (50, 844) 2-chloro-5-methoxy-3,6-diphenyl (1.1 equivalents of 20% methanolic sodium methoxide at 135° for 20h) (797) 2-benzyloxy-6-chloro(at reflux) (832, cf. 883) 2-chloro-3-pyridinio(pyrazine)chloride (or tosylate) (to give 2,3-dimethoxypyrazine) (765) ... 

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