The structural properties and binding motif of a strongly σ‐electron‐donating N‐heterocyclic carbene have been investigated on different transition‐metal surfaces. The examined cyclic (alkyl)(amino)carbene (CAAC) was found to be mobile on surfaces, and molecular islands with short‐range order could be found at high coverage. A combination of scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations highlights how CAACs bind to the surface, which is of tremendous importance to gain an understanding of heterogeneous catalysts bearing CAACs as ligands.

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 cis‐selective hydrogenation of abundant aryl boronic acids and their derivatives catalyzed by rhodium cyclic (alkyl)(amino)carbene (Rh–CAAC) is reported. The reaction tolerates a variety of boron‐protecting groups and provides direct access to a broad scope of saturated, borylated carbo‐ and heterocycles with various functional groups. The transformation is strategically important because the versatile saturated boronate products are difficult to prepare by other methods. The utility of the saturated cyclic building blocks was demonstrated by post‐functionalization of the boron group.

Aza-Diels-Alder reactions (ADARs) are powerful processes that furnish N-heterocycles in a straightforward fashion. Intramolecular variants offer the additional possibility of generating bi- and polycyclic systems with high stereoselectivity. We report herein a novel Brønsted acid catalyzed process in which ortho-quinone methide imines tethered to the dienophile via the N substituent react in an intramolecular ADAR to form complex quinolizidines and oxazinoquinolines in a one-step process. The reactions proceed under very mild conditions, with very good yields and good to very good diastereo- and enantioselectivities. Furthermore, the process was extended to a domino reaction that efficiently combines substrate synthesis, ortho-quinone methide imine formation, and ADAR.

We report an enantio-and diastereoselective, complete hydrogenation of multiply substituted benzofurans in a one-pot cascade catalysis. The developed protocol facilitates the controlled installation of up to six new defined stereocenters and produces architecturally complex octahydrobenzofurans, prevalent in many bioactive molecules. A unique match of a chiral homogeneous ruthenium-N-heterocyclic carbene complex and an in situ activated rhodium catalyst from a complex precursor act in sequence to enable the presented process.

The chiral ruthenium(II)bis-SINpEt complex is a versatile and powerful catalyst for the hydrogenation of a broad range of heteroarenes. This study aims to provide understanding of the active form of...

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...

Aza-Diels-Alder-Reaktionen (ADARs) sind leistungsfähige Prozesse zum schnellenu nd stereoselektiven Aufbau von Stickstoffheterocyclen. Intramolekulare Varianten bieten darüber hinaus die Mçglichkeit, bi-und polycyclische Ringsysteme in einem Schritt mit hoher Stereoselektivitätz u generieren. In dem hier entwickelten Brønsted-Säure-katalysierten Verfahren kçnnen nun erstmals ortho-Chinonmethidimine,d ie über den Iminsubstituenten an ein Dienophil gebunden sind, in einer enantioselektiven ADAR mit inversem Elektronenbedarf zu komplexen Chinolizidin-und Oxazinochinolin-Ringsystemen umgesetzt werden. Die Reaktionen laufen unter milden Bedingungen in sehr guten Ausbeuten und mit guten bis sehr guten Diastereo-und Enantioselektivitäten ab.D as Verfahren kann darüber hinaus zu einem Domino-Prozess erweitert werden, der Substratsynthese,o rtho-Chinonmethid-Bildung und ADAR effizient vereinigt.