Alcohol tosylates from

After decarboxylation, enolization in the alternative mode would cause racemization. However, this reasoning does not explain why 199 was racemized. The racemic a-aminoketones were eventually resolved via their bromocamphorsulfonates. Optically pure (—)-indolizidin-l-one (196) was reduced with lithium aluminum hydride to the alcohol, tosylated, and again reduced to (+)-indolizidine [Eq. (28)]. Since indolizidine obtained from R-pipecolic acid [Eq. (29)] was levorotatory, it followed that the absolute configuration of the original ketone was S.254 The optical rotatory dispersion (ORD) curve of the S(-)-ketone showed a strong negative Cotton effect as predicted by the octant rule. 

We have focussed on alkyl halides but tosylates from TsCl and mesylates from MsCl can be used too. The conversion of alcohols to chlorides and bromides is discussed earlier in this chapter and the combination of reagents used to make thiols is discussed in the next chapter. 

Problem 16.9 You prepare 5ec-butyl tosylate from alcohol of [aj +6.9 . On hydrolysis with aqueous base, this ester gives A c-butyl alcohol of [a] - 6.9 . Without knowing the configuration or optical purity of the starting alcohol, what (if anything) can you say about the stereochemistry of the hydrolysis step ... 

Tosylate esters may be prepared in the absence of pyridine as solvent by converting the hydroxyl group to a lithium salt by addition of methyl or butyllithium. The resultant lithium alkoxide is then treated with tosyl chloride. This approach is recommended for the preparation of tosylates from very sensitive alcohols, provided that they do not contain other functional groups that react with the alkyl lithium reagents. 

Sulfur example—formation of a tosylate from toluenesulfonyl chloride and an alcohol ... 

Several reducing agents have been utilized to remove tosylate esters of sugars and other polyols. In particular, lithium aluminum hydride and lithium triethylborohydride have been most extensively used [20-23]. When secondary alcohol tosylates are used, epoxide intermediates are frequently involved. Reduction is observed to occur through either C-0 or O-S bond cleavage [24]. In this chapter, we discuss our results from the reduction of 6-0-tosylates of D-glucal and D-galactal with lithium aluminum hydride in THF. 

A mixture of 0.30 mol of the acetylenic tosylate (prepared according to the general method described in VlII-3, Exp. 3 from the corresponding acetylenic alcohol, which was prepared from HC=CHgBr and CgHi3CH=0 in THF, as described in Ref. l)and 100 ml of dry acetone was added to a solution of 0.40 mol of anhydrous... 

An advantage that sulfonate esters have over alkyl halides is that their prepara tion from alcohols does not involve any of the bonds to carbon The alcohol oxygen becomes the oxygen that connects the alkyl group to the sulfonyl group Thus the configuration of a sulfonate ester is exactly the same as that of the alcohol from which It was prepared If we wish to study the stereochemistry of nucleophilic substitution m an optically active substrate for example we know that a tosylate ester will have the same configuration and the same optical purity as the alcohol from which it was prepared... 

Section 8 14 Nucleophilic substitution can occur with leaving groups other than halide Alkyl p toluenesulfonates (tosylates) which are prepared from alcohols by reaction with p toulenesulfonyl chloride are often used... 

This sulfonyl urea, prepared from an amino acid and p-tosyl isocyanate in 20-80% yield, is cleaved by alcohols (95% aq. EtOH, n-PrOH, or -BuOH, 100°, 1 h, 95% yield). It is stable to dilute base, to acids (HBr/AcOH or cold CF3CO2H), and to hydrazine. ... 

A -Oleflns in the 5a-series are frequently formed by elimination from the tosylates of 3j5-alcohols. Contamination with A -compound is common, and puriflcation via a derivative (e.g. dibromide) may be necessary (see page 343). A 2-methyl substituent increases the selectivity ... 

The elimination of water from a fluorinated compound generally follows a reaction path similar to that of its nonfluorinated counterpart, although the presence of the highly electronegative fluorine atoms may have unexpected effects Various monofluoro alcohols can be dehydrated via their tosyl esters at 75 C by using potassium rert-butoxide [80] (equation 50)... 

---