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, Brønsted 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.

All-c-multifluorinated cycloalkanes exhibit intriguing electronic properties. In particular, they display extremely high dipole moments perpendicular to the aliphatic ring, making them highly desired motifs in material science. Very few such motifs have been prepared, as their syntheses require multistep sequences from diastereoselectively prefunctionalized precursors. Herein we report a synthetic strategy to access these valuable materials via the rhodium-cyclic (alkyl)(amino)carbene (CAAC)-catalyzed hydrogenation of readily available fluorinated arenes in hexane. This route enables the scalable single-step preparation of an abundance of multisubstituted and multifluorinated cycloalkanes, including all--1,2,3,4,5,6-hexafluorocyclohexane as well as cis-configured fluorinated aliphatic heterocycles.

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We report a method to convert readily available silylated arenes into silylated saturated carbo- and heterocycles by arene hydrogenation. The scope includes alkoxy- and halosilyl substituents. Silyl groups can be derivatized into a plethora of functionalities and find application in organic synthesis, materials science, and pharmaceutical, agrochemical, and fragrance research. However, silylated saturated (hetero- ) cycles are difficult to access with current technologies. The yield of the hydrogenation depends on the amount of the silica gel additive. This silica effect also enables a significant improvement of a previously disclosed method for the hydrogenation of highly fluorinated arenes (e.g., to all-cis-C H F ).

Recently, chemoselective methods for the hydrogenation of fluorinated, silylated, and borylated arenes have been developed providing direct access to previously unattainable, valuable products. Herein, a comprehensive study on the employed rhodium-cyclic (alkyl)­(amino)­carbene (CAAC) catalyst precursor is disclosed. Mechanistic experiments, kinetic studies, and surface-spectroscopic methods revealed supported rhodium(0) nanoparticles (NP) as the active catalytic species. Further studies suggest that CAAC-derived modifiers play a key role in determining the chemoselectivity of the hydrogenation of fluorinated arenes, thus offering an avenue for further tuning of the catalytic properties.

A novel and practical chiral ruthenium-NHC-diamine system is disclosed for the enantioselective hydrogenation of isocoumarins, which provides a new concept to apply (chiral) NHC ligands in asymmetric catalysis. A variety of optically active 3-substituted 3,4-dihydroisocoumarins were obtained in excellent enantioselectivities (up to 99% ee). Moreover, this methodology was utilized in the synthesis of O-methylmellein, mellein, and ochratoxin A.

The enantioselective synthesis of tetrahydroimidazo[1,2-a]pyridines by direct hydrogenation was achieved using a ruthenium/N-heterocyclic carbene (NHC) catalyst. The reaction forgoes the need for protecting or activating groups, proceeds with complete regioselectivity, good to excellent yields, enantiomeric ratios of up to 98:2, and tolerates a broad range of functional groups. 5,6,7,8-Tetrahydroimidazo[1,2-a]pyridines, which are found in numerous bioactive molecules, were directly obtained by this method, and its applicability was demonstrated by the (formal) synthesis of several functional molecules.

We report a method for the enantioselective hydrogenation of annulated arenes using 4H-pyrido[1,2-a]pyrimidinones as sub-strates. The method selectively generates multiple stereocenters in adjacent rings leading to architecturally complex motifs, which...