Alcohol kinetic resolution

Mikolajczyk and coworkers have summarized other methods which lead to the desired sulfmate esters These are asymmetric oxidation of sulfenamides, kinetic resolution of racemic sulfmates in transesterification with chiral alcohols, kinetic resolution of racemic sulfinates upon treatment with chiral Grignard reagents, optical resolution via cyclodextrin complexes, and esterification of sulfinyl chlorides with chiral alcohols in the presence of optically active amines. None of these methods is very satisfactory since the esters produced are of low enantiomeric purity. However, the reaction of dialkyl sulfites (33) with t-butylmagnesium chloride in the presence of quinine gave the corresponding methyl, ethyl, n-propyl, isopropyl and n-butyl 2,2-dimethylpropane-l-yl sulfinates (34) of 43 to 73% enantiomeric purity in 50 to 84% yield. This made available sulfinate esters for the synthesis of t-butyl sulfoxides (35). 

Kinetic Resolution by Direct Esterification. This is the least common strategy for kinetic resolution and is most commonly executed on racemic alcohols with carboxylic acids in organic solvents. Reports include several alicyclic secondary alcohols such as menthol and various aliphatic secondary alcohols. Kinetic resolution of a variety of racemic saturated, unsaturated, and a-substituted carboxylic acids has also been effected by direct esterification with various alcohols. ... 

Whereas primary aUyl alcohols may be converted to the extent of 100%, for secondary alcohols, kinetic resolution is used to obtain one diastereomer in excess. The J. T. Baker Company harked back to the original work of Sharpless [194] and developed from it an industrial process for the production of (+)-dis-parlure. 

A number of other asymmetric enolate protonation reactions have been described using chiral proton sources in the synthesis of a-aryl cyclohexanones. These include the stoichiometric use of chiral diols [68] and a-sulfinyl alcohols [69]. Other catalytic approaches involve the use of a BlNAP-AgF complex with MeOH as the achiral proton source, [70] a chiral sulfonamide/achiral sulfonic acid system [71,72] and a cationic BINAP-Au complex which also was extended to acyclic tertiary a-aryl ketones [73]. Enantioenriched 2-aryl-cyclohexanones have also been accessed by oxidative kinetic resolution of secondary alcohols, kinetic resolution of racemic 2-arylcyclohexanones via an asymmetric Bayer-Villiger oxidation [74] and by arylation with diaryhodonium salts and desymmetrisation with a chiral Li-base [75]. 

In the late 1990s, several research groups worked on the development of chiral DMAP analogs. The works of Fu [23], Vedejs [24], and Fuji [25] led to the synthesis of powerful catalysts and the development of enantioselective organocatalytic reactions such as Steghch rearrangements, kinetic resolutions of secondary alcohols, kinetic resolution of amines, and so on (Scheme 1.8). 

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