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This Article details the development of the iron-catalyzed conversion of olefins to radicals and their subsequent use in the construction of C-C bonds. Optimization of a reductive diene cyclization led to the development of an intermolecular cross-coupling of electronically-differentiated donor and acceptor olefins. Although the substitution on the donor olefins was initially limited to alkyl and aryl groups, additional efforts culminated in the expansion of the scope of the substitution to various heteroatom-based functionalities, providing a unified olefin reactivity. A vinyl sulfone acceptor olefin was developed, which allowed for the efficient synthesis of sulfone adducts that could be used as branch points for further diversification. Moreover, this reactivity was extended into an olefin-based Minisci reaction to functionalize heterocyclic scaffolds. Finally, mechanistic studies resulted in a more thorough understanding of the reaction, giving rise to the development of a more efficient second-generation set of olefin cross-coupling conditions.

A novel methodology for the synthesis of 3,3-difluoropiperidines has been developed. The target compounds are prepared in three steps using a robust protocol and simple starting materials. The incorporation of the fluorine is achieved by using the cheap and easily available ethyl 2-bromo-2,2-difluoroacetate as building block. Using this methodology, a new potent in vitro phosphodiesterase 2A (PDE2A) inhibitor containing the functionalized fluorinated piperidine scaffold has been prepared.

Recently, the direct substitution of allylic, benzylic, and tertiary alcohols has been achieved via SN1-type reactions with catalytic amounts of Bronsted 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 catalysis) or chiral electrophiles (iminium catalysis, chiral counterion catalysis) can easily be generated. Recently, we have used stabilized carbenium ions, directly available or obtained from the corresponding alcohols, in new organocatalytic stereoselective SN1-type reactions. The commercially available carbenium ion benzodithiolylium tetrafluoroborate 1 can be used for the straightforward organocatalytic stereoselective alkylation of aldehydes. 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.

The stereoselective alkylation of aldehydes with benzodithiolylium tetrafluoborate gave a straightforward access to key compounds for the synthesis of fragrances and flavors.