R -2-Octanol

The opposite enantiomer (R)-2-octanol is obtained in 77% yield after removal of the acyl group, as shown in Fig. 4. The purity of 99% and the enantiomeric ratio of R S 99.5 0.5 (determined by chiral GC) is also excellent. The acylated (R)-2-octanol is obtained as the first intermediate in the above-mentioned lipase-catalyzed reaction in MTBE and has to be separated from unreacted (S)-2-octanol. 

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Problem 14.14 (R)-2-Octanol and its ethyl ether are levorotatory. Predict the configuration and sign of rotation of the ethyl ether prepared from this alcohol by (a) reacting with Na and then CjHjBr (b) reacting in a solvent of low dielectric constant with concentrated HBr and then with CjHjO Na. ... 

The example given in the text illustrates inversion of configuration in the SN2 hydrolysis of (S)-( 1 )-2-bromooctane, which yields (R)-(-)-2-octanol. The hydrolysis of (R)-( )-2-bromooctanc exactly mirrors that of its enantiomer and yields (S>(+)-2-octanol. 

In Section 8.14 of the text we are told that optically pure (S )-( I )-1-methylheptyl /Holuenesulfonate is prepared from optically pure (S)-(+)-2-octanol having a specific rotation [a]o +9.9°. The conversion of an alcohol to a p-toluenesulfonate proceeds with complete retention of configuration. Hydrolysis of this /Holuenesulfonate with inversion of configuration therefore yields optically pure (R)-(-)-2-octanol of [ ]d -9.9°. 

Reaction of (R)-2-octanol with p-toluenesulfonyl chloride yields a p-toluenesulfonate ester (tosylate) having the same configuration the stereogenic center is not involved in this step. Reaction... 

Stereochemical consequences of 5 2 reactions on derivatives of (R)-2-octanol. Substitution via the halide gives a product with the same stereochemistry as the starting alcohol substitution via the tosylate gives a product with opposite stereochemistry to the starting alcohol. 

A final example involves the enantioselective polymerization of racemic 10-hydroxyundecanoic acid by CRL (Scheme 11.8) [31], The polymerization reaction was stopped when 50% monomer conversion was reached and polymers with a molecular weight of lkgmoT (PDI = 1.3) were isolated. Subsequent H-NMR analysis using the Mosher s acid derivatization procedure on the residual monomer and hydrolyzed monomer revealed an ee of 33 and 60%, respectively. Comparison with Mosher s esters of R-2-octanol and rao2-octanol showed that the S-monomer was preferentially incorporated in the polymer. 

Optically active secondary alkyl halides. Landini et al have extended their study of the conversion of methanesulfonates to alkyl fluorides to the reaction of the methanesulfonate (1) of (-)-(R)-2-octanol with KF, KCl, KBr, or KI in the presence of a phase-transfer catalyst in a two-phase system. In the case of... 

There appear to have been no further studies on the thermal decomposition of alkyl nitrites until 1949. Then two more complex nitrites were studied. Komblum and Oliveto (1949) examined the thermal decomposition of optically active 2-octyl nitrite in the liquid phase at 100°C. Optically pure r(-2-octanol was obtained in excellent yield, thus showing that 2-octoxyl radicals were produced, and that these did not racemize. 

Optical intereonversion of sec-alcohols. This reaction can be accomplished readily by treatment of the salt (a, above) with trichloroacetic acid and triethyl-amine to give the ester 2, with inverted configuration. Alkaline hydrolysis of 2 then affords the alcohol 3. A typical example is the conversion of (R)-(—)-2-octanol into (S)-( + )-2-octanol, formulated in equation (I). 

Fig. 8-1 Reduction of2-octanone to (R)-2-octanol. Substrate-coupled NADPH regeneration [51].

The nature of the chiral derivatization reagent is critical in achieving optimum resolution of the diastereomers, and for simple carboxylic add reagents containing a phenyl or other 7t-donating group close to the chiral centre are recommended to improve the resolution. This effect was particularly well demonstrated by Kaneda [59], who showed that the S(+)-2-butanol (20) or R(—)-2-octanol (21) esters of 2-methylbutyric add were unresolved by gas chromatography but the esters with R- -methylbenzyl alcohol (19) were readily separated. (See Section 4.2.2 for the numbered structures). 

Despite 1,2,4-oxadiazoles being highly efficient in promoting mesomorphic behavior, they are generally achiral calamitic molecules. To achieve the noncentrosymmetry necessary for FE behavior, a chiral alkoxy chain derived from (R)-2-octanol has been introduced into the structure of calamitic LCs derived from 1,3,4- and 1,2,4-oxadiazole, resulting in formation of the first chiral oxadiazole-based LC exhibiting FE properties (2008LCl251). 

The following sequence of steps converts (R)-2-octanol to (S)-2-octanol. 

The observation that R-2-octyl acetate yields R-2-octanol with 99% retention rules out the possibility that the reaction occurs by alkyl-oxygen fission [10]. This mechanism is consistent with the normal mode of ester hydrolysis which also occurs by acyl-oxygen fission. Neither amides nor nitriles were affected by superoxide under phase transfer conditions [10]. The data on ester cleavage by superoxide ion is summarized in Table 8.3. 

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