Abstract Arene hydrogenation provides direct access to saturated carbo- and heterocycles and thus its strategic application may be used to shorten synthetic routes. This powerful transformation is widely applied in industry and is expected to facilitate major breakthroughs in the applied sciences. The ability to overcome aromaticity while controlling diastereo-, enantio-, and chemoselectivity is central to the use of hydrogenation in the preparation of complex molecules. In general, the hydrogenation of multisubstituted arenes yields predominantly the cis isomer. Enantiocontrol is imparted by chiral auxiliaries, Br?nsted acids, or transition-metal catalysts. Recent studies have demonstrated that highly chemoselective transformations are possible. Such methods and the underlying strategies are reviewed herein, with an emphasis on synthetically useful examples that employ readily available catalysts.

Piperidines and fluorine substituents are both independently indispensable components in pharmaceuticals, agrochemicals and materials. Logically, the incorporation of fluorine atoms into piperidine scaffolds is therefore an area of tremendous potential. However, synthetic approaches towards the formation of these architectures are often impractical. The diastereoselective synthesis of substituted monofluorinated piperidines often requires substrates with pre-defined stereochemistry. That of multifluorinated piperidines is even more challenging, and often needs to be carried out in multistep syntheses. In this report, we describe a straightforward process for the one-pot rhodium-catalysed dearomatization–hydrogenation of fluoropyridine precursors. This strategy enables the formation of a plethora of substituted all-cis-(multi)fluorinated piperidines in a highly diastereoselective fashion through pyridine dearomatization followed by complete saturation of the resulting intermediates by hydrogenation. Fluorinated piperidines with defined axial/equatorial orientation of fluorine substituents were successfully applied in the preparation of commercial drugs analogues. Additionally, fluorinated PipPhos as well as fluorinated ionic liquids were obtained by this dearomatization–hydrogenation process.