Helicene based alcohol

Scheme 2.75 Synthesis of an enantiopure helicene-based alcohol.

As mentioned previously, the helicene-based chlorophosphite M,M,R) 25a, which is easily prepared from the reaction ofenantiopure (M,M,R)-[5 -HELOL 24a with phosphorus trichloride, has been successfirUy used to analyze the enantiomeric compositions of a variety of chiral materials such as alcohols, amines, or carboxylic acids. The reaction is conducted in an NMR tube where the analytes are added to the chiral helicene-based chlorophosphite in CDCI3. After 2 h reaction, the diastereomers ratios generated in situ are determined by P-NMR spectroscopy. Notably, this attractive method has proved to be highly efficient for analyzing the enantiomeric purities of a wide range of molecules whose stereogenic centers are far away from functional groups that react with phosphorus atom. The authors... 

The Friedel-Crafts diannelation in the first step was based on Flellwinkel and Schmidf s methodology for [4]helicenes, except for the use of alkenes instead of alcohols as the precursors to the intermediate carbocations (Section 15.2.1) [70]. 

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