Rhodium(CAAC)‐Catalyzed Arene Hydrogenation of Benzo‐Fused N‐Heterocycles to Saturated Building Blocks with an all‐cis Configuration

Abstract

Saturated carbo‐ and heterocyclic building blocks can be readily obtained by the hydrogenation of aromatic carbo‐ and heterocycles. Although a variety of methods have been established to accomplish this transformation for simple arenes, the hydrogenation of aromatic N‐heterocycles is less explored. We herein report a diastereoselective arene hydrogenation which was applied to an array of benzo‐fused N‐heterocycles. A total of 48 saturated heterocycles was obtained by hydrogenation in the presence of the rhodium complex Cy(CAAC)Rh(cod)Cl in yields of 72–98% with moderate to high diastereoselectivities exhibiting the hydrogen atoms in an all‐cis arrangement. The high tolerance towards functional groups enables the formation of valuable saturated products, which offer a starting point for further derivatization.

cis-Selective Hydrogenation of Aryl Germanes: A Direct Approach to Access Saturated Carbo- and Heterocyclic Germanes

“…Herein, we describe the first comprehensive study for the direct preparation of diastereoselective saturated carbo-cyclic germanes including the unprecedented preparation of valuable saturated heterocyclic germanes via the additive-free hydrogenation of aryl germanes. Previously, the groups of Zeng et al, , Bullock et al, , Andersson et al, our group, ,− ,− and others − have reported novel catalytic arene hydrogenation reactions using rhodium and ruthenium metal-based catalytic systems. Intrigued by these reports, we examined the hydrogenation of aryl germanes employing various molecular complexes and heterogeneous metal species as catalysts.…”

Photochemical Deracemization of 3‐Substituted Oxindoles

“…Attempts to completely hydrogenate the benzo ring of oxindoles resulted in low diastereoselectivities when Rh/C [16] was employed as catalyst. The known carbene complex Cy (CAAC)Rh(cod)Cl [17] gave better results and enabled the conversion [18] of oxindoles 1 r and 1 p with a notable diastereoselectivity (Scheme 3).…”

Access to C(sp3) borylated and silylated cyclic molecules: hydrogenation of corresponding arenes and heteroarenes

“…26 Glorius' catalyst was utilized by Bach's group to hydrogenate one borylated 2-oxindole among other benzofused N-heterocycles, 2,5-diketopiperazine, and 3,4-dihydroquinolones. 27–29…”

“…26 Glorius' catalyst was utilized by Bach's group to hydrogenate one borylated 2-oxindole among other benzofused N-heterocycles, 2,5-diketopiperazine, and 3,4-dihydroquinolones. [27][28][29] Glorius also reported hydrogenations using Rh/C in their optimization studies on six borylated substrates (ve benzenes and one pyridine). 21 Catalysis with Rh/C showed full conversion with TBS protected 4-Bpin phenol, but as the authors noted the other arenes tested and the pyridine gave diminished yields (17-33%).…”