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ABSTRACT Recently, the direct substitution of allylic, benzylic, and tertiary alcohols has been achieved via SN1-type reactions with catalytic amounts of Brønsted or Lewis acids. When a new stereogenic center is formed most of these transformations produce the desired product as a racemate, as these reactions proceed through carbenium ions. The arsenal of activation modes available in organocatalysis can be used to set up suitable reaction conditions in which chiral nucleophiles (enamine ) or chiral electrophiles (iminium , chiral counterion ) can easily be generated. Recently, we have used stabilized carbenium ions, directly available or obtained from the corresponding alcohols, in new organocatalytic SN1-type reactions. The commercially available carbenium ion benzodithiolylium tetrafluoroborate 1 can be used for the straightforward organocatalytic . In this account we will illustrate the application of this methodology in the total synthesis of natural products and the preparation of valuable starting materials. Chirality 26:607-613, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Diastereoselective SN1-type reactions have been known for many years and have been used in the synthesis of many natural products. It has recently been shown that chiral nucleophiles, obtained using organocatalytic methodologies, can react with highly reactive carbenium ions in a stereoselective fashion. Based on this, carbenium ions can be applied in asymmetric catalytic reactions. [ABSTRACT FROM AUTHOR]